I ran her account through TwitterAudit, which is a site that can tell you if an account is fake or how many fake followers and account has. Right now it says that 60% of her followers are real and 40% are fake.
I did the same thing 2 or 3 years ago and posted the results. I think it was on TOS. I don't remember the exact numbers, but I'm pretty sure her percentage of fake followers was quite a bit higher back then. IMO the reason you see a decrease in followers since her high mark of 49k in 2015 is because she probably deleted a bunch of the ones that were bad, obvious fakes in order to get her percentage of fake followers down.
I'm sure she's picked up some new real followers since she started this city council run. But the only other time she has gotten any real traction online that would have resulted in Twitter follows was when the Gamergate fiasco happened in late 2014. She probably picked up some followers then who were actually real people which explains part of the increase in followers between Jan 2014 and March 2015.