I'm just worried about her. The mechanic said it could do a lot of damage if she continues to drive it. Work and home is a 30 mile round trip, but she's been going places and hour or two away, so i know she's putting some heavy highway miles on it.
Wouldn't you feel guilty if you knew of a potential hazard and did nothing to warn them??
I just don't see how buying a computer is going to benefit her in any way. There's so many things that should have higher priority.
You did warn her of what the mechanic said. You have done what you can.
The computer likely is a wasteful decision but it is her decision. You're not her mother. You can't make her do anything she doesn't want to do.
You did your best to tell her about it, if it falls on deaf ears there is nothing more that you can do. It's now time to concentrate on YOU and moving on with your life. Somewhere out there is a girl that deserves a great guy like you. Keep your chin up, she'll be out of your home soon and once she is, in all honesty, I'd cut contact with her completely. She's not coming across as a healthy person to be around.