Since the daughter is in college, one would assume she is around her 20's. Taking that fact, I'm guessing that her dad is someone old. Why is this fact significant? If, and only if, the OP is telling the truth, then I conclude that her father is someone that either owns the Celtics or is on the coaching staff. The players are way too young to have a daughter in her 20's.
Now, around the 40-60 age range, that narrow it down to Doc Rivers, Danny Ainge, Tom Thibodeau, and Armond Hill. Since Ainge was still in the hospital tonday (at least I think so), that narrow it down to the coaching staff. I'm gonna take a stab in the dark and say her father is either Doc or Tom Thibodeau. I assume it's the latter.
All of this, of course, is assuming this story holds any legitimacy.