AITA for giving up and putting my dog down

Aita for putting my 8 year old pitbull lab down due to her aggressive behaviors? Everyone that I tell that I’m putting her down says that I should just try this or try that or that I just need to keep working with her and I’ve had her for so long with the same behaviors and they’ve just progressively gotten worse I have a five year-old daughter loves her to death, but one of the dogs triggers are that she scared of bicycles and it’s hard to have a five year old and a dog that doesn’t like bicycles. Another issue is that she bites my dad and hospitalized him while he wan on a bicycle and she continually attacks my other dog. And I know what you’re thinking maybe the other dogs causing it when in all reality it’s not. she will get grouchy enough overnight and try attacking the other dog in his sleep unprovoked. before now about three or four years ago, she bit my horse and tried to pull me off of him. She has recently bit my fiancé after being disciplined for bad behaviors or after a fight. so I’m just wondering, am I being a shitty person for putting my dog down?