Sorry, OP, sounds like a hard situation for you. 50 cents a mile is pretty steep for a teen, too. But I don't know what to suggest.
We've bought two vehicles for our girls and we pay all expenses. DH uses those vehicles for occasional running around too, and I didn't want to make them pay for his use, nor did I want to keep track of it. Oh, and there are lots of times she drives her sister somewhere, such as the 70 mile round trip to drivers ed several times last summer. This is also our way of letting them save for college, since we don't have college funds for them. But they don't abuse it, either. If they were putting on the miles your daughter is, we would have to come to some sort of compromise. We are rural, too, it's 11 miles to school and their friends are all at least 11 miles away, some up to 25 miles away. And I don't want to "punish" them for being country dwellers by keeping them home when their friends go out. So far their driving has been within reasonable limits. DD18 is one of the oldest of her grade, but until recently she had a very small friend group that didn't do much outside school and no one was asking for rides. DD15 has a lot of friends but is one of the youngest, so by the time she has her full license, everyone else will have their license already. So I guess we lucked out.
We have a 1999 Dodge Dakota ($3400)and a 2003 Jeep ($6800) so they are older but we found them with low miles so we hope they last a long time. Problem is, the Dakota is RWD with a big engine so it's terrible on snow. DD18 can use the Jeep in winter weather while she is still living at home, but next year we have to decide if she needs AWD/4WD at college. The Jeep will stay here for her sister. If we decide to get something else, we will probably pay for the 4WD for DD18, and her pickup will stay here for DH to use. We were thinking an older Equinox or something that can serve her well at college and beyond. She loves her yellow pickup though!