It is not going to be a gusher...not like having her period. A towel under her and a panty liner will most likely be all she needs.
Am more concern about the blood, how do we stop it?
Don't forget a condom and some lubricant that won't affect the condom. And like jefelex said....slow, slow slow but at some point you just have to go for it but wait until SHE says for you to do that. Also, yes, make sure this is right for the both of you. Don't pressure her. If she is not ready, then that's it and you have to respect her wishes. Oh, and "pop my gfs cherry" well...that does sound a bit crass.
Don't brag about it, also ensure that you love her completely before you make her commit to having sex with you - it's a lot bigger deal for the woman than the man, and the pain and bleeding is something she will have to deal with, but you'll have to support her to the best of your ability. Don't be a jerk about it, make sure you communicate with her, love her and go ever so slowly.