In my experience, girls with a great takeoff can transition from the 12' to 13' poles relatively easily, but girls who tend to be flat at takeoff do much better on 12'6 poles. Gill makes 12'6 Mystics and PacerFXs. The weight label is right at the top, so your max handhold would be about 12'4, maybe a little higher. Spirit makes 13'1 poles with the label 6" from the top, so your max handhold is 12'7 or so.
For me, I had trouble rolling over the 13' Spirits when I was gripping less than 12'. I jumped better on my 12'6 poles... and I was amazed throughout college at how many of my female teammates jumped significantly better on 12'6 poles than they did on 13' poles.
12' Spirits tend to run pretty stiff, if you went with a 12'6 Mystic, you'd probably want a 125 or 130. If you went with a 13' Spirit, it's probably going to be a jump from a 12'120 to 13'120. It would be tough to go with an even bigger jump than that...but with the amount of time you have left, it would be nice to have at least a 125 just in case you gain more muscle....
If your club had a 12'130 Spirit you could borrow, it would make the transition to 13' poles a lot easier.