DS is 8mo, and when we're at PILs house (about once a week), MIL will very often start feeding him random food. Usually it's ok, although sometimes it's stuff that's not that healthy. Is it weird of me to wish she'd ask me first? If she did ask, I'd usually say yes, although there have been a few times when I've asked her to only give a spoonful (eg to let him taste something new, but unhealthy), and she's just kept spooning it on in.
I just find it a bit rude. We're doing blw, so I try to limit purees (so he doesn't get used to just sucking food in), but she'll give him stuff like that. She also, for example, gave him lots of jelly one day (ignoring me when I asked her to stop), so then he didn't want any milk all evening, and then was hungry during the night.
My own mum would always ask before giving him anything at all, and if she does offer to give him something it's always vegetables or fruit, not sweets. I'd never give food to someone else's child without permission.