Here's my full story-
I wanted to meet Merida when I went in July. It wasn't my top priority but still on my bucket list. It's my last day at the parks, so I figured I'd hop in line in the afternoon and wait it out. Throughout the week, I kept seeing the long lines and telling myself "Oh, I'll just come back when it's shorter", but it looked like the sky was about to open up so I figured it was now or never.
I ended up waiting about 30 minutes. The CM was warning us that if the thunder got much closer, they'd have to shut down the M&G and we wouldn't be able to meet her unless she re-opened (which she probably wouldn't have for the evening). Luckily, I was the last one allowed into the M&G area that evening.
They were rushing her to get through all of us in the area in time, and she was really sweet. She hastily signed a little girl's autograph book even though her CM shouted at people to just take a photo and leave. When it was my turn, she welcomed me with a hug and apologized for being rushed off. She explained that the CMs were only worried about everyone's safety, and noticing that I had curly hair she joked "and you KNOW how our hair gets in this weather!". I asked her how she kept her curly hair maintained and she told me she used spring water before we snapped a quick pic and she was rushed back inside.
In the end, I think my quick little meet with her was worth the time I spent waiting, but maybe not the stress. If you notice the weather has been iffy, and you have another day at MK, I'd try another attraction. If not, wait it out in the long lines. The queue isn't even that bad.
Sorry for the really long story!