my cats temper has changed

Question
I got my cat at 8 weeks old she is now almost 2 years old she is a very loving cat and great with my son.she use to be so good when my friends and family would come over she would pur at them and lay on there laps then outta no where one day my sister and her bf came over and she was hissing growling and scratching and biting at them and she has know them since she was a kitten she goes after my father in law and all my friends and for some weird reason when we have others in our home she will hiss at me and my husband to but as soon as my company leaves the cat is good with us again :(

Answer
Wow, this is a weird behavior change. The first question I always ask if they are fixed? Cats have a behavior change when something is going on with them and they have no other way to tell you than to act different. Something in the environment has changed or she's not feeling well. Since she's fine when you have no company, I would say that's not the case. It's obvious that she does not like company anymore for some reason. I would suggest getting a product called Feliway. It's a synthetic product that portrays the natural cat scent. I would use that just before company comes over. You can also incorporate the spray bottle, but I fear that would add to her anger. Does anyone do anything before she reacts or does she react instantly? When your sister and bf came over, were they trying to hold her or did she attack? One thing you could try is having them toss her a toy or a treat so that she can associate them with something positive.

This really is a puzzle as we don't know what is triggering her actions. Keep me posted and see if we can't think of something else to try. I feel this is going to be a trial and error situation.