First allow me to say that I'm impressed that you both are waiting until you're 18. Trust me it's worth the wait.

To answer your first question:

It's hard to say whether or not her hymen is broken. Consider that your index finger is about the same size as a tampon, and that those don't tend to break it.

To answer your second question:

It's also hard to say. I had a girlfriend in college who would gush torrents of sweet nectar when she came, and a few towels placed "downstream" would be enough. This is usually referred to as female ejaculation. It's not pee, as some would have you think. It's a clear liquid.

But I would say that the vast majority of women don't experience this. Most just get wetter (like my wife) and a towel right under her or some such is more than enough to catch anything.

My advice: Don't worry about it. Let her come! Neither of you will not regret it!