In my opinion...
Most women do not give such importance to cllmax. some just do not cum at all, or do very seldom, and this does not bother them. Men are different, they get that "unfinished" feeling lingering on . This fits with nature's plans, male's cllmax is needed. But a woman can be fully satisfied without reaching cllmax. I believe that women often feel having their cllmax as a "duty", because men are so concerned about the matter. Being a woman I don't feel my cllmax being the most pleasant moment of sex. In my experience I often felt that men are obsessed with pleasing their women in a "standard" way, which means having an cllmax, and they easily get upset or deceived if she doesn't cum. But nature makes woman's pleasure much more intense and satisfying, while man's pleasure is concentrated in a few seconds .
The matter is that men worry too much about this and so they push their women to fake. But everyone should be free to enjoy sex his/her own way, there are no rules to follow.
If yr girlfriend says she is satisfied, you should believe her. If you think she might fake, well, i think she will never admit such a thing! Women do not fake because they do not please, they do because they please their way( which likely isn't a standard way) but do not want to deceive partner nor to go under "trial" because of that. Try to give less importance to the "cum" matter, she will feel more free to express herself and be honest with you.
PS a lot of women fake... this makes saying the truth even more embarrassing, just as if it was about being a freak or a frigid.