My sister in law has ruined their finances.

This is my view too. I learned the hard way from my dad.

I was ok giving the money, I knew I likely wouldn't get it back. That's why I didn't give them the amount they wanted. I just also got blindsided by us also losing a car in the process.

Also, the real kicker is that they don't even need another vehicle. She just wants one. The only place she ever goes is to her mom's house. She's currently using her mom's extra car anyway.

It's just frustrating all around.