The visuals for this comic were a bit tricky to figure out, but I'm pretty happy with the results.
For people who love numbers, Catalina's wound up at 1/7 scale (or about 14.286% normal height, and about 0.29% overall size). This is MUCH more shrinking than Tedd can currently manage.
MANY people predicted that Rhoda thinking "it will be mutual" would result in both of them shrinking. From an in-universe perspective, the reason there was no risk of that happening is visually apparent: Rhoda uses her hands to focus on her spell targets.
Whether this is required or simply helps her focus her magic is questionable, but the end result is that her resizing has targeting assistance.
Elliot, meanwhile, is susceptable to thoughts interfering with his transformations because he has to imagine how he's going to look. With practice, he could prevent "sabotoge", but he's not there yet. In any case, that sort of sabotage isn't applicable to Rhoda, or at least not applicable in this instance.