I like your 3D pen. Never seen anything like this before. It looks pretty cool. I'm thinking you might be able to draw some flowers..different color including grass and put it in a little holder. It might look cute and your sister might like it.
Good luck. Have fun.

Check me out over on Platforms Discord https://discord.gg/TJMWMVD, you might find better ideas for your pen from other members there, and you might earn some Platforms tokens, SBI or free votes for just talking.