If it is just a fiberglass bath tub, you can just use nail polish remover.
nail polish remover
Nails polish remover or hot water. You can soak your nails in hot/warm water and take an electrical nail file and remove it. Or you could be cheap like me and rub it off with nail polish remover. Depending on the nail glue that you used, non acetone nail polish remover usually works the best.
The solvents used in nail polish and nail polish remover is the most likely answer
Used in nail polish remover
acetone
nail polish, nail polish remover, hairspray, hair product, Vaseline, any chemicals, 3M Dust Remover, etc...
I would use nail polish remover that is 100% acetone. I have used nail polish remover on linoleum tile and laminate counter tops to remove wall paint and it worked great. I just tried nail polish remover on the tile in my bathroom and it was fine. You won't have to worry about damage. If you are worried about damage try it on a little spot that isn't too visible first.
It dilutes the acetone
I just used nail polish remover on my black leather chair and ottoman (made by Ashley)to remove pink nail polish and it worked without damaging the leather.
Basically how you get rid of nail polish when it's on your skins/nails. You can put the nail polish remover on the stain or put more nail polish on top of the stain and wipe it off quickly. This worked for me.
It contains "ACETONE", Water, hydrolized collagen, glycerine, and usually fragnances