24 married child eligible for FSA of parent?

If a 24 year old gets married are they still eligible for parent’s FSA? Even if they are no longer a tax dependent?

Yes, assuming plan allows for it via eligibility definition.  Being married is not relevant.

Nor is being a tax dependent. I was able to cover my daughter, living and working full time hours with multiple employers (gig economy free lancer) in another state until she turned 26, four years after she stopped being a dependent.