Here are some ways you can ask her to be your girlfriend:

1. Call her and ask her directly.
2. Send her a musical note or a song that expresses your feelings.
3. Write a poem or a letter that tells her how you feel.
4. Give her a sweet treat or her favorite flower with a note that says "Will you be my girlfriend?".
5. Sing it to her or play her a poem.
6. Involve her special people, such as her friends or family, and ask them to help you.
7. Sweep her off her feet at the end of a romantic date and ask her.

Remember that it's important to be clear and direct so she knows exactly how you feel. Look her in the eyes and say something like, "I've really enjoyed being with you. Would you be my girlfriend?" or, for something more casual, say, "I want to get to know you better. Want to go out?"

I hope this helps! Let me know if there's anything else I can do for you.