Women are with that are meeting her needs. You can't make any assumptions about how a woman might react given a set of circumstances unless you know what her needs are.
When women run hot and cold, what is happening is what is important to her on any particular week will change based on where her emotions are taking her. I've seen this time and time again. But she will always drift back to her core values developed when she was younger. The hotter she is the more apt she will bounce around, because she can get away with it because people will always make excuses for her, and she can always find some dumb@ss willing to sacrifice for her.
As she ages, her baseline needs will change, and if you can not adjust to her changing requirements, then you just have to walk away. Look... you DO NOT want a 'loyal' woman in your life if you can not meet her needs. You see this all the fvcking time with miserable marriages, if her needs are not being met... she will morph into a fat nagging b1tch, torturing you because you can't or will not meet her needs. She's 'loyal' because she ain't going nowhere, she'll stay around an beat you into submission. LOYALITY is an over rated value when it comes to women.