I doubt im the only person that had this happen, but at least for me whenever i skipped and event that I had already seen mia would just be on my screen at all times and would overlay with herself whenever I went to do a transformation. This is on the web version so that probably has something to do with it
I was redoing the mind control on Mia for the petplay content and when I skipped the first one event for the mind control she was just stuck on my screen
Edit: I just went back to the web version and checked to see if the glitch was still there, but when I loaded in she wasn't stuck on my screen anymore. I tried resetting and doing the first mind control one but I was unable to get it to happen again.