Nasty a$$ diaper week

So this week I started getting this 9 month old from about 10:15 til 3:30.  Her mom dropped her off yesterday and not even 5 mins later I was smelling something kinda funky.  (As a mom you know what your own child's poopy diapers smell like, and this was not Teagan't funky butt lol.)  Anyway I checked Aliyah's diaper and omg she had squirted out the sides, up her back, everywhere.  Thankfully her mom had an extra set of clothes in her diaper bag like I ask there to be in case of explosions such as these.  I changed her, and I felt so bad cuz her little butt was so red.  I thought, wow if she just pooped, what in the world did she eat that made her butt so red?  My daughter would have poopy diapers and if we got to them right away her butt wouldn't be red unless she had something somewhat acidic to eat.  anyway i didn't think much of it.  Well today she got here and the second I picked her up after he mom left (which was just 2 mins later) I smelled that she had pooped.  Same thing, it was everywhere.  Now I am starting to think her mom just puts her in her carseat and brings her here, even though she knows she pooped.  I have to say something to her today cuz it's just not right and Aliyah's butt is so tender and it has to hurt ya know?  I just don't like telling parents what to do because being a parent, I get easily irritated when someone tells me, You should/need/have to do this blah blah blah.  But this seems kind of...neglectful in a sense and maybe she doesn't realize that her daughter sitting in a poopy diaper for even 5 mins is going to cause irritations and if her skin is sensitive, it is that much worse.  Sigh...I feel so bad for Aliyah...I am checking her every 15 mins or so to make sure her diaper isn't wet, cuz I keep putting cream on her at each change to hopefully help get rid of the rash.