Dog euthanasia after biting

My dog bites.. but let me explain:

My dog was traumatised after a neighbour let her out of our garden, she was chased and grabbed at my strangers. So now obviously she’s mistrustful of strangers and always has a guard up – understandable. We’ve spent thousands on training and socialising her after this. She’s on expensive antidepressants. She is muzzled every time she’s outside. I feel like I’ve tried everything to help her understand she doesn’t need to resort straight to biting.

She has bitten my MIL, 2 strangers, my auntie, and now the dog walker who she loves. I don’t know how much more of this I can take and I don’t know what to do anymore. Her biting is almost always defensive, and if she bites it’s usually when I’m not around. I understand this isn’t her fault, it’s mine. However I wouldn’t be able to live with myself if she managed to bite a child, the guilt I feel is horrible.

She is a strong and powerful dog and she can and has done some damage with my MIL needing stitches in her hand. I feel as though now she’s a ticking time bomb and I can never trust her in public spaces. As far as training and medication goes I’ve spent so much time and money trying to help rehabilitate her I don’t know if I have anything left. Which is horrible I know, I love her so much but what else can I do?

My husband has had enough, we have held off having children due to having this dog. Advice would be greatly appreciated TIA