How do I make my girlfriend less sensitive?

So my girlfriend is very sensitive all over her body including her nipples and clit. While this is hot for most of the time we're having sex, it's nearly impossible to make her orgasm because when she's well on her way she'll just become extremely overstimulated and need to stop whether it's clitoral stimulation or penetrative. It's so bad sometimes that even with my nails cut as short as I can, she says that she can still feel my nail beds and that it's uncomfortable for her. She says that she still enjoys sex for the most part but I know that both of us would like for her to be able to orgasm.