Many girls in my own area wouldn't want BTC as a present on any event but the one's that actually know the value like yours will really appreciate it.
In most areas, whether girls or boys as long as they don't know the true value of Bitcoin. They will have to decline the offer even if it's a gift. You present them with a $5 and a 0.001 Bitcoin and they'll choose the $5 cash.
In experimental videos that I have watched. Most women that have been presented with cash and bitcoin have no idea of what bitcoin is. The most of them chose to have plain cash than Bitcoin.
This gesture is a good thing and OPs girlfriend is aware of what Bitcoin is and hopefully she don't get rekt with her trades.