I guess I'm looking for some advice.... I'd like to be supportive, and help her get back on track by helping to resolve the issues that make doing her homework so hard now. But I don't see how I can still let her go to the party.
Personally, I think it would be a mistake. If you punish her by not allowing her to attend her best friends 16th birthday party, she may really rebel about everything. Since she is not talking about her feelings with her parents, she needs someone who will listen and support her. Her friend probably does, but I suggest you check with the school counselor and see if she will feel free to talk. If s/he is only an academic counselor, then seeking a family therapist may be in order.
She is the innocent that gets hurts in the fallout of her parents' disaster. It's probably hard for her to find motivation to even do the homework, when she feels her world falling apart. Let her know you are concerned for her emotional well being b/c you love her. You want her to feel free to go to you about anything......not keep secrets b/c she's afraid you'll punish her.
I tried very hard to put your suggestions into effect. I had a long talk with her, let her know I loved and was concerned for her, and let her go to the party. We discussed consequence v punishment and how she couldn't stay at her friends house because then she'd be too tired to do her homework today.
When I picked her up, she was happy, sweet, and friendly, so I guess I did some things right.
Today, she was focused, and got a lot of homework done. And I even took her for a session with a counsellor.
M:23 T:26 Me:53, Wife: 60 S:18 D:16 filed 7/16 W moved out 4/28/17
