Our new adopted dog Hannah

Question
My name is Chris and my husband and I have just adopted cute Hannah (mixed Poodle/Lapso)Hannah is 5 and a female who we rescued from the Riverside Humane Society about four weeks ago. Let's not forget about our current kid named Cassie she is 11 years young and just lost her 13 year old best friend named Ducie of cancer (our parents dog). We wanted another companion for her to play with and hang out with. We brought Cassie with us to meet Hannah they hit it off no signs of aggression etc. they told us that Hannah may be a little snotty at first when meeting a new dog but no sign of that at all when they met. Hannah was at the Humane Society for 5 long weeks and not one person looked at her they said because she was 5 years old and most people wanted puppies and much younger. We saw her cute face on line and my best Friend who lives in Riverside went to meet her before we went to see her just to make sure she might be a match for our family and she was. We found out that Hannah was an only dog (pet) and that the older lady went into a nursing home and could no longer take care of herself or Hannah anymore. Also, found out after the fact that Hannah was not socialized either where as Cassie very much is.

We brought her home and the first week it was the best they were great both no signs of any problems at all. Hannah had free rain throughout the home as Cassie does but that all changed during the second week. The second week we noticed snarling and growling at Cassie during play time and especially during dinner. But we immediately got Hannah's attention when the "aggression" started to show by touching her or snapping our fingers even saying "no' just to stop her focus on Cassie. Then the 3rd week came and Hannah started attacking Cassie out of the blue when ever she wanted to get water, was walking by John or I and especially at dinner time that was the worst. One day last week I was outside filling the water bowl and Hannah attacked Cassie and ripped under her eye open, then again attacked Cassie just yesterday when she was walking by the couch heading to her bed and when my husband John pulled her off, Hannah bit John a few times (no blood drawn). We have several comfie beds set up all over the house so what ever room they may be in they can each relax in comfort and water bowls also in different places especially now that Hannah prevents Cassie from certain areas of the house.

Last Saturday, we were at wits end after Hannah bit Cassie we took Hannah to Petco and were going to get her fitted for a muzzle so she would not attack Cassie anymore. We ran into "a Petco on Staff" trainer who spent three plus hours with us and Hannah and said that she is definitely aggressive towards other dogs and most sure never been socialized as well. Gave us a lot of tips and also told us to get a "Haltie" to put over muzzle designed like a horse halter so when she snarls or growls we are to quick jerk it to get her attention defocused away or to take two fingers and touch her neck when doing that during her aggression times. So far so-so she still growls when we do it and when she does not have the Haltie on we don't trust her but we don't want to keep it on all the time my husband says he thinks that he can control the situation during play time and feeding time (he is SOO wrong).

Let me explain about my husband, John has Multiple Sclerosis and is disabled not wheelchair bound but house bound most of the time in and out of bed sleeping all throughout the day due to his debilitating disease. The worst attack on him is heat and "STRESS" any type of Stress sets off his disease and this has been absolutely stressful on him dealing with this daily over the last three going on four weeks especially when I am at work 8 to 10 hours a day. John needs the companionship Hannah so loveling provides when he is in bed all day long she lays by his side since Cassie has a hard time coming up stairs (old age) John is happy to have someone there. Cassie is not at all jealous she just sleeps and relaxes all day downstairs or outside basking in the sun what ever she feels like doing comes and goes and she pleases. Where as Hannah has to be around us all the time. Also when Hannah growls or snarls we discipline her by putting her outside on the back patio for up to 15 min since was told to do that to show her she was bad and that being away from us is a form of punishment (per Petco Trainer).

My husband and I are very active in the community and we donate our time and love to several organizations that help with the homeless dogs in our community of Ventura, CA. We pick up donated food from Petco and Petsmart and deliver to Catholic Charities and S.P.A.N. who pass out Dog Food and other pet items to the homeless for their pets so they have a good quality of life as well. We feel the same for Hannah we want her life to be full of happy times she deserves it as all animals do and we have lots of love to give her since we have no children of our own we think of them as our kids. We have never owned two dogs and are at wits end on how this is going to work out we cannot continue having Hannah attack our cute 11 year old Lovable Labrador Cassie that is not fair to her, we need help and guidance or someone to tell us that it will or won't work or what is best for Hannah for her to be happy also.

We have set up for dog training classes through Petco starting this Sat. but only for 6 weeks once a Sat. and we need help ASAP now do you have any suggestions on what we can do to help our "stressed out family" I cannot allow this to keep continuing on for my Husbands health has been effected and Cassie's life and my own sanity is at stake.  

Answer
I am happy you provided so many details, but I am not sure I have a good answer.  The rational thing is to return Hannah to the shelter and try a different dog.  We aren't always able to do the rational.  

5 year olds can be very set in their ways, and slow to change.  A good obedience course should help.  The key to most behavior problems is approaching things using the dog's natural instincts. Dogs see all the people and dogs in the household as a pack with each having their own rank in the pack and a top dog. Life is much easier if the 2 legged pack members outrank the 4 legged ones. You can learn to play the role of top dog by reading some books or going to a good obedience class. A good obedience class or book is about you being top dog, not about rewarding standard commands with a treat. Start at http://www.dogsbestfriend.com/ For more on being top dog, see http://www.dogbreedinfo.com./topdogrules.htm