Scarlet, I have big issues with seeing a situation not as all good or all bad as well. Even if I understand it rationally, the feelings either are all black or all white. I think realizing that there is good and bad to it, even though our emotions say otherwise, is the first step to actually feeling it as well. But of course it's still very though, it doesn't just go away.
I can understand how though it is for you to have L not around for a while. I'd feel abandoned too, as well as the other things you're describing. It's hard that you're currently already going through a lot and now this is piled on top. I hope that you both still have time to make arrangements for the time where she's away. I think that you need a stable environment for therapy and shouldn't have to think too much about L's issues. When is the next time you guys can talk?
Also, while I'm not generally a fan of your H, for once I agree with him and am glad he's trying to be supportive. I wouldn't worry too much about the SH right now.
It is a coping skill that while maladaptive, your body currently doesn't have better skills to use and it does relieve stress. Just try to focus on treating yourself well for now.