Where does it say she was divorced? The other references to this woman are all past tense as well. There are many reasons for divorce aside from sexual incompatibility, though it is evidently a big reason for many.
The rest of this comment is inspiring and positive and should be more popular, since it's something that OP could actually use. If OP's relationship has lasted 6 years already, there is clearly a stronger base to it than just sex.
Personally, I don't agree with the comments encouraging a break up over this. Communication and clarity and working through a struggle together can save a relationship, and there are ways that OP can be satisfied within the relationship in a healthy way, they just need to find them - and work with their girlfriend to do so.