How much porn do you watch and how rough are you with your dick when you masturbate? Being very wet is from being turned on, some women get wetter than others. Without much info, it could be that it's "too wet" but it sounds to me like it could also be your dick that's desensitized.
If she is truly very very wet, you could bring it up and you can adjust, like wipe a bit of it off. Don't ask her to wipe it all off because obviously that wouldn't feel good and hurt for her. Again, you're saying she's too wet but it could be you, not her, but no one can confirm it either way.
I don't know your age but I've found some guys have some pretty weird beliefs/expectations about women and sex that come from porn and that aren't realistic. Women in porn often look super dry. That would feel awful.
Also, there's no rule that you must finish in a specific way. If it's difficult finishing from sex, then finish another way. Unless she's part of the minority of women who orgasms really easily from penetration, I doubt you're changing what feels good for you because that's how she expects to finish. If you can't finish that way, is there any other way you can finish? Hand (hers, yours with her assistance), mouth, boobs..?
(Mods, not sure if this is allowed - apologies and please delete if not permitted)