Can a check payable to "Mother, FBO daughter" be cashed or deposited in the mother's account, or does it need to be deposited in an account titled the same way?

You wouldn't want to negotiate a check like that through the mother's account. It may be titled that way because it is UTMA funds and they have to be structured in an account of that fashion.

Now if they know that it isn't a UTMA or the check doesn't indicate that this is the situation, you should be able to have the mother sign the check over to herself, but that to me would still be iffy.

I would just make sure that it isn't meant for a UTMA first then go from there.

I've seen checks of that title used by the parent to pay for college expenses. Not saying that's the right way to handle them, but I document they were used for the child's benenfit.