Wondering if I really make my gf cum

My girlfriend has been with men before me, and I’m a stud. Every girl I’ve been with before has told me they came from me fingering or eating them out, but my current girlfriend has more sexual experience than my previous partners, so I keep worrying that I’m not enough.
She tells me she cums every time we’re together, but part of me wonders if she’s just saying that to make me feel good.
We were also talking about getting a strap, and she said she thinks a 7-inch one would be good. What confuses me is that she can’t comfortably take two fingers sometimes, so I’m struggling to understand how that would work.
My questions are:

If someone says they orgasm every time, should I trust that unless they’ve given me a reason not to?

Is it normal for someone to feel pain with 2 fingers but want a 7 inch strap?

Has anyone else dealt with insecurity because their partner had previous experience with men? How did you get over it