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. I would like to say you did well and thats because the person you gifted knows it value and now my only curiosity is what she is gonna do with this gift like, would it be a start for her to start saving up BTC as an investment plan ?Or she would just sell it off in the exchange and use it as fiat and get something because Ladies are fund of wanting flashy things.
If I must be honest with you, I did tell you that, not everything is meant to be given as a birthday gift, and bitcoin is one of those stuffs, whether the person understand or knows the value of it or not, bitcoin is not ideal, or suitable to be given as a birthday gift, most especially to a lady..
You said it yourself, and it is also known generally that women like flashy things, and as such, no matter the value of bitcoin given to a lady as a birthday gift, she will still appreciate that physical gift that is shiny and worth almost nothing, more than the bitcoin given to her at that very moment the gift is given...
My advice is, when considering giving a lady bitcoin as a birthday gift, consider attaching a small physical gift by the side.