Is libest du meine tochter also fine?
"Libest" is not a legit word. It's "liebst" (and it's accepted.). In addition, you should write noun (Tochter) in capital, even though Duolingo makes no difference about it.
In fact, I'd say that's probably a more common way to say it, since you probably know someone rather well, if you're asking them that question.
Yea, I agree.
Liebst was NOT accepted. It said the plural lieben was correct with singular you. That makes no sense to me.
"Liebest" is conjunctive, which does'nt make sense in this context :)