Your mom is probably depressed and desperate right now. Seems like she and your father have some major financial issues and she's taking responsibility of the debt for your dad's decision, which stressed her out enormously. She needs therapy.

But this is NOT your fault. Having bad grades is not uncommon among kids. You have your kid problem to overcome -- get your grades up, and she got her own problems. But it's not right for her to abandon her kids. I feel she's more trying to get your dad in some way.

You didn't not fuck up, your parents did.

She's probably having a break-down and will collect herself together soon.

Hugs to you and your sister!