I don't know the answer to your question about a trust, but I will suggest that you think about what you intend to do and why you are doing it.
If you want to give the child a gift, I think you should give it without a contingent plan to take it back. You could give her a savings bond.
If you want to save money that you may or may not someday use to contribute to the child's education or whatnot, open a savings account in your own name and start squirreling away money without making some big announcement that the account belongs to her.
A child who has already gone through her parents' divorce doesn't need their new girlfriends and boyfriends making promises of support and then taking them back later.