If I forfeit a car but have a co-signer, are they still expected to pay?

I’ve been thinking about filing for a year now, but one situation has me unsure what to do.

When I was 18, my sister and I bought a car. We were desperate and didn’t know any better at the time and didn’t have anyone to advise us otherwise.

Technically it’s my sister’s car, but they put the car in my name and listed her as the cosigner (likely bc I had older credit than her).

Anyways, they sold us a lemon with a 26% interest rate. Still owe $20k, $800/mo payments that she’s fallen behind on and I can’t afford to cover.

My car has a 6% interest rate and only owe $7k left with no issues, so it would make more sense to keep my car if I have to forfeit one.

She’s fine with forfeiting her car, but she’s worried she’ll still have to pay the full price when she can’t afford to and have no car to show for it. The cars only worth $3k.

I’m worried about any repercussions since she’s the cosigner. If I were to forfeit the car would she still have to make payments on it despite not having it? Has anyone dealt with filing bankruptcy when they have a cosigner? I plan to make a consultation just want to know if anyone’s dealt with this or knows what would happen!

(I plan to try for chapter 7 and am in Maryland)