Her schedule is worse than Ayame's. At least with Ayame you can set your expectations accordingly and are mentally prepared for her to take a lot of time of. Ayame will come visit you once in a while and that's what you're used to now. Mito will just randomly show up at your door and say hello, but then when you wanna lead her inside, let alone even have her get her foot in the door, she's gone again. But then she comes back!... a week later, or two weeks later, or 3 days later.
Basically what I'm saying is that, being regular > being irregular