Must a parent continue to pay child support once a child enters college?

It depends on the terms of the support agreement. As a general rule, there is no legal obligation for a parent to support adult children, including paying for their college. Once a child is 18, a parent may put them on their own. However, it is also legal and not uncommon for a child support agreement to specific support past 18 (including, for example, paying for college). So the support agreement needs to checked, but if there's nothing in there, then no, he should have to pay once she is an adult.