You've only been away one week. If D5 is doing well at your mom's home that tells me it's an okay place to be. D3 may take a bit longer to come around. She will though.
You are the grown-up. You are a good mother. I base that opinion of you on your other posts. Give yourself more time. When you are upset, D3 is going to sense that. She'll react to your emotional state whether you are at your mom's or you own home.
I encourage you to do some fun activities with your girls especially D3. You don't have to spend a lot of money. You can color together, make cookies, make play dough, draw pictures, make collages out of magazines--anything that gets your minds off the down side of your situation. Maybe grandma would like to play too?
As my mother used to say, "Little pictures have big ears." In other words make sure D3 is well out of earshot when you discuss AH and other issues with your mom and your friends. This is important.