S.B.
I have not read your prior posts about these custody issues, but if you are getting an agreed upon amount of child support and benefits (ie insurance),I am not comfortable with you having access to accounts that have been set up for your child's future benefit. My guess is that grandparents have set up a college fund for your daughter?? Who claims your daughter on their taxes as a dependent? If any of the accounts are in her social security number and generate taxable income, then a 1099 (i think that is the number) is issued.
It would depend what type of accounts they are and what type of restrictions the accounts have (like a 529 education account available in some states) on whether you could have access to them.
Of course, best case scenario would be that they would share the information with you that they have funds for future education or a future car.
But I sense your relationship with the "exes" may be poor and they won't give you access to those accounts.
Would I use the money? Only if I could not feed or house my child. I would feel like it would be stealing from the child's future.