I'm gonna make it simple...

A) She still lives under her father's roof, so IT IS his business, particularly if she's underage, which I'm guessing she is.
B) Her father probably paid for that laptop and he no doubt pays the internet bill too.
C) Her father has good reason to be wary of older guys around his daughter, as all fathers do. If he didn't care, I wouldn't have any respect for him.
D) PAY ATTENTION TO THIS ONE -- If she's as young as I'm guessing she is, she will use you as a means to get out from under "mean old dad who spoils all my fun"'s roof. And she'll then expect you to take care of her. And it could get uglier than that. If you knock her up, don't expect it to last. Don't say it won't happen either. And then you're going to be paying child support for the next 21 years (if the case is heard in NY, yep, 21 years not 18 . And worse, if she decides she hates you, expect her to turn that "my father abuses me" thing into "my ex-boyfriend abused me." DON'T SAY I DIDN'T WARN YOU!!! Sure, not every girl does this, but I've seen it happen. Like firsthand. More than once. Your life will be hell for the next 21 years. So my advice would be...... stop thinking with your dick and RUN!