Why is it that (many) women hold grudges and get jealous so quickly?

At times, I find it very excruciating at times dealing with women, my fiancée in particular. She will hang onto old baggage from bad relationships and refuse to drag them out of her emotional closet to the curb for pick up, she might for a moment, but then drag them back in. Many times, she had been cheated on, and treated very badly by the chuckleheads she was involved with before we met. Somehow, I have to keep sweeping those bad issues away. I did not make the mess but I seem to be the one always with the broom in hand cleaning up the mess. Why do (many) women have to hang on to all that funk of the past, to the point they think any woman you know, you are going to try and cheat with them as ______, ______, and ______, etc. did before you?