The amount of money you spend to acquire important knowledge (lessons) is the cost of your education. You have learned an important lesson (not to be a wise guy, but Ben Franklin already told you) about lending. That's the kind of money you lend a spouse or a person who signs a contract acknowledging the debt. I do not know what the amount of money can be adjudicated in small claims court, but I would explore that arena, in case a big split happens before the settlement happens, you have it on record that she owes you the money. If you know what insurance company is involved, and if you can get the case number, you may be able to place a lien on any disbursement that pays you first, before she gets a dime. Pretty iffy. But, here's the way you should look at it:

"The fact that you are/were my gf when I paid for your lawyer because you drove drunk and wrecked the car has nothing to do with the fact that the lawyer cost three large, which you owe me. We had no agreement that I would cover your expenses, legal or otherwise".

I guess it's just up to whether you want to work for this money again, as it were, or whether the idea that this -ahem- person thinks she is entitled to almost 4k of your money. Yours.

If it were me, and I saw her with one mental foot out the door, I would make sure that she understands that I'm coming after her for it, she can make it easy on herself, or difficult. Although you are not an incorporated entity, you may be able to list that debt on her credit report, it being related to a legal matter, IDK.

I've lost money, $300, $500, not enough to get lathered up about. But even if we just go 3k, depending on what you do, that can represent a lot of labor. I'd want it back.