Thanks for the info.
I bit the bullet and washed them and put them on her. She definitely has some room to grow in them, but they're not crazy big. She's 22 lbs and just getting into 18 month clothes, but the smallest they had in the store was 2T. I know I can get 18m online, but I didn't want to waste money if they were as small as all the other Gerber stuff.
It's getting pretty warm here now, so I just leave her in those and a shirt.