Ditto. I have acrylic over my nails and they are never sharp even though they're long. I never had a problem fingering myself or another girl with them but when I finger my husband's ass I'm more careful and I use a finger cot and lots of lube just to make sure I don't hurt him.
In Joost Zwagerman's novel "The Outside Woman" one woman had long nails on all fingers but her index specifically to be able to finger her mans ass while giving head. I found that fascinating. Lot of obscene details in that book...
My wife has long finger nails and never has a problem. I also have longer nails on my right hand (for classical guitar playing) and she has never complained. Mine aren't any more than about a 1/4" at max though.