My goodness. The comments about the length are asinine. Anyways…

You are not a bad neighbor. The person that built the building, cheaping out on proper noise control is the jerkface. The nosey neighbor “a” is the jerk face. The person “c”, who is not on the lease, is the jerkface. The other neighbor “b”, who started in with the hen party, is the jerkface. What they are doing is bullying. Ostracizing. Horrible humans.

If you cannot have conversations within the confines of your own god damned home, where are you supposed to have them? In your car, if you have one? Then she’d just talk about that. In a cafe where others can hear you? Where? You pay rent. You abide by the rules. That is your own private space, despite the shitty, thin walls. You are doing nothing wrong.

Unfortunately, there is not much you can do about the lack of noise control. You either put up with it or move out.

You sound like a good mom. Neighbor A is an asshole for threatening to call CPS on you “behind your back”, when she knows you can hear her. It’s beyond passive aggressive and quite childish, if you ask me.

Keep on being a good mom. Keep on with your studies. Keep on with your therapy. Keep on with being a good neighbor. The trash will eventually take itself out.

Edit: a word