How about setting specific and limited times to get or give help. Say at 10:30 there will be a half hour help break and then again at 2:00 or whenever. Post the times. That way if she really needs help she gets some but the time frame is limited. Then don't let the time run longer than the stated time. Or not by much.
Then if she asks at another time you can point to the next available help time and you can tell her the rest of the time is ME time, which is why you come.