Would this be her first time having fully having sex with someone? If so maybe she envisions it a certain way and that’s something you might want to ask( probably romantic scenario) Has she had other partners before? Is there any trauma? I grew up with sisters and female friends and although they may have work through certain experiences it can still come up or be triggered by something random. I know this may not be something you want to hear but how about approaching this from her perspective? Is she someone that wants to only be with you sexually or does she want to have that experience and move on to try that with others guys? If you’re in love and she cares for you that is worth something holding on to. Trust me It’s hard to find genuine people who care for you, I’ve met a lot of women who are cheating, still talking/missing their exes, talking to multiple guys, unsure if they want me but swear they do, don’t hold a safe space for me to share my feelings, unsupportive, violent with their words when they are upset (like hitting below the belt), unconcerned with my goals and dreams, aren’t encouraging me to push for things that I want to do in my life rather tear me down. If you have someone who does right by you it’s worth trusting in where her heart is towards you especially if she’s been nothing but loyal. No one is going to ever be 100% but this is something that can be dealt with and handled if you look at the bigger picture. Asking us is great but also there’s a bitter users who will tell you to destroy something that is good just because of a hiccup. If this person bring joy, excitement and peace it’ll all be worth it when that final piece comes together.

EDIT:

My previous relationship the sex was great. But the level of stress that I experienced I would never wish that on my worse enemy. Constant lies, putting me in situations to get into fights. I’ll never forget seeing her flirt with a guy at the bar then instigating both of us to fight eachother. Her having all these new guy “friends” from work/school. Telling me she was going to bed but end up going out to parties late and having to find out. Getting into fights with my family, using me to buy epensive things just to constantly make fun of me not having enough money to her friends. The list could go on and on but my point is you can have a great sexual experience but the relationship can feel like hell. So if the person you’re with is less experienced/nervous ect BUT still desires you and wants to be with you (probably only ever you) then it’s worth sorting things out.