In my experience....females start to reach breeding size at about 30 months.
I have had a few go as early as 18 months but it is the exception rather than the rule. (at least it is here)

For me, for a ball python to be "breedable", I have to have the right mix of size and age.....and I think way too many people disregard the age factor (especially with females.....males are a different story). Young female bp's just seem goofy. They go against all the "rules", often showing atypical breeding behaviors, and just drive me nuts.

One bit of advise....ditch the "with my/her current progression" approach. I'm not trying to be rude or anything but I gave it up a long time ago and it is one of the things that kept me sane Just when you think you have ball pythons figured out, they have a way of making you humble.

Good luck with your girl.....I hope she does go for you next year!