Thanks for the advice.

I have talked to my girlfriend and decided that when she's ready for a bike, I'll purchase one for her - but she'll have to pick it out and the choice is hers. I'll have enough money by the time she's ready to buy her something she wants and not worry about the price. It just won't be a surprise.

I tried surprising her with an engagement ring and that got messed up - but I won't get into that here, just throwing that out there as I would like to do something nice and have it be a surprise.