son, listen to MuscleMom and the other girsl, you asked the question, maybe you should have done a little more research before posting on a forum such as this. Why wouldn't you ask an older brother or friend about this sublect? I missed how old you are, but it sounds like your WAY to young to get married if you still have questions like this. Do you not have any girl friends? I know you had a mother, she would have filled you in to some degree, not to mention your dad I hope.
As you have read, the hyman is'n connected to an artery or anything. So, no, it's not going to spurt blood everywhere like a pumpping open wound! IF, and I say IF, she still has one that is connected, don't act like a scared little boy having his first sexual experience, simply ask her if she would prefer that you use a towel, just in case. My guess is that she'll think your cute for asking because it has been years since she first started masturbating and that she has been using "toys" for years. She knows what she has or has not done to herself. But as posted previously, most break from normal physical activity, even if she hasn't had a "toyfriend" before.
Read M-moms and the other girls posts again, they'll tell you straight.
Tx