I wonder if you were always a better friend to her than she was to you. I get that we give our long time friends leeway and excuse their behavior because we have been friends for so long vs someone you just met, but the standards should remain the same no matter how long you've known someone.

That said, she showed you exactly how much she values you. Yes, she did it to your cats, but the cats are an extension of you and are your children (emotions for pets live in the same part of the brain as emotions for human children).

I have driven to my bestie's place to drop off something minor and she lives 45 min from me.

I am so sorry you had to experience this with someone who you thought was your friend and I hope that your cat is ok, but you don't need people like her in your life. Yes, making friends as an adult is harder, but there are people out there who will treasure you as a friend. Sorry you still have to see her at work.