not a great career

I agree that her career was much better than the OP seems to think. You hit most of the high points, though I also enjoyed Kiss of the Dragon and the true guilty pleasure that is Lake Placid.

I do think it's a bit of a shame that she decided to call it quits when she did. She was a solid talent with a distinctive look, and I always enjoyed watching her perform. But as you say, she went out more or less in her prime and there are certainly worse ways to do it.

https://www.quora.com/Why-did-Bridget-Fonda-suddenly-stop-acting/answer/Jon-Mixon-1

One reason that is rarely touched upon was her overall lack of financial success as a performer. Bridget Fonda just didn’t bring home “the bacon”.

In 2001, Fonda starred in three films, none of which did much at the box office. Her major film of that year, Monkeybone was such a significant disaster that it caused her co-star Brendan Fraser, to be ousted from his spot on the Hollywood A-list. Even her turn with, at the time, up and coming action hero, Jet Li, did poorly and it had a budget that was negligible.

It seems likely that following her vehicle accident in 2001, and after she married composer Danny Elfman in November of that year, Fonda made some difficult calculations regarding her career. She wasn’t going to be an A-list draw, the roles coming her way were likely becoming “Mommy” ones, and she was approaching 40. Since she was pretty well off herself and Elfman’s net worth is substantial, she likely decided to let her career “cool down”.

It’s also likely that as time passed, she decided that she no longer wanted (nor needed) the aggravation and humiliation that comes with being an aging female performer in Hollywood and simply decided to “retire”. Since her peers at the time are now themselves either semi-retired or underemployed, it seems that she made a very wise decision.