If your mom is into unique funky polishes I would suggest going the indie route with some polishes that have glitter or are just sort of wacky. Model City Polish, Finger Lickin' Lacquer, Nail Pattern Boldness, and Carpe Noctem Cosmetics on Etsy have some great stuff, as does Lucky 13 Lacquer.
I would also suggest getting in contact with /u/kyoti, /u/ninakasper, or /u/riotcoming about possibly making a custom for your Mom. They are three of the shop owners of the above shops I listed.
Beyond that I think a nice basket of supplies, like a glass nail file or two, some acetone if she has natural nails, maybe some cuticle oils from Emerald&Ash in her favorite scents. (I really recommend the Blood Orange with Cinnamon) Check out Amazon for cute nail decals and gems for added bling and as little extras to add into her basket.
I use this book for nail art inspiration. It's easy to follow and has fun designs.
I hope this helps you out and don't forget to wrap everything well in bubble wrap and in really cute tissue paper and maybe some ribbons. Having something to unwrap that's girly and frilly can lift a mood as well as the present you get!!
Update and give us pictures!!