It's up to you, if you make it known her father knows (if you keep it that he does) but if the Doctor finds out, he's going to want to leave ASAP, repercussions and all of her father finding out. Or there's the whole "make her parents super drunk" after Summer assured them or told them whatever it is she wanted to say to them, since they really haven't talked all that much, as I wondered, what you wanted Summer to say or do with her parents. But if they got drunk, it's more likely that they wouldn't remember a future Summer and thus her time line stays in tact?