jealousy and aggression Border Collie

Question
Hi,we adopted a Border Collie female called Meg 7 months ago,she is 5 yrs old.Her owner passed away and he trained her really well we are not sure if she did any field work, as he was an elderly man. Meg has settled wonderfully we have found her to be very laid back and gets on with dogs when off the lead shares her toys but we have found just in the last month when we have her on the lead she wears a gentle leader by the way,if we stop to talk to anyone with a dog she is wanting to attack it's like the devil is in her.I cannot believe she is this gentle Meg who is wonderful with everyone and children,we went on holiday about 3 weeks ago and she came with us we were worrying a bit but needn't have she loved it,then we went to stay for a couple of days with friends they have a greyhound who is an old chap called Badger, she knows him they have a holiday home next to us so plays out with him.Anyway she started showing her teeth and every time he was near her in the garden and house even my friend was surprised at this. Since she came back we can't hug or talk to anyone without her having a bark or getting between us we are ignoring and not making eye contact she just wants to play all the time we hide her toys and she gruffs and pants but we stand our ground.I want to be able to stand and talk to anyone we meet with or without a dog without her trying to get attention all the time we don't spoil her she 's not getting treats unless she obeys a command. A long walk in the morning playing outside and walk and run on the beach at t- time. I think because she had our attention 24 hrs a day on holiday she has got a little cocky now, we have had a border collie before but from a pup she was different again.Our main problem is not letting this pulling on the lead and  jealousy get the better of us please help thankyou

Answer
Hi Gillian -

Congrats on your new pup.  This is a very serious problem.  I recommend that you consult with a trainer in your area for advice and support in this matter ASAP.  That being said Border Collies are a wonderful breed. They are high energy and need large amounts of exercise, from what I've read, up to two hours a day.  It sounds like she gets quite a bit of exercise with you, however this breed is VERY active.  Without enough exercise (all dogs are individuals so while 1 hour might tire out one border, another might need 2 hours of work) they can become destructive and aggressive.  If you google temperment of a border collie there are quite a few articles discussing how the breed can become aggressive.  I have included a link below to get you started.  Please consult a trainer to help you re-establish yourself as leader.  Things like putting her in a sit/stay before going outdoors or getting fed can help.  Take ownership of everything and make her work for it.  Remember nothing in life is free so petting, while satisfying to humans, should be earned by the dog. Make her do a command before offering affection.  Training should be reward based and positive.
It sounds like you're doing everything right and that she is becoming possessive of you, her home, and toys.  You have experience with the breed, but remember all dogs are individuals.  I think working with a trainer for a few sessions who can observe her body language and the situation first hand will help you resolve your issue.  Remember that Meg was in a previous home so these issues may have been present in her first life and are resurfacing now.  Best of luck resolving your issue, don't give up on your girl!

http://www.dogtemperament.com/border-collie-temperament/