Well I think they would get along I mean there really isn't much to fight about in the first place...but I think this situation would have to happen..because I find it hard to speculate because anything could happen.

I don't see how anything bad could happen

I have no idea really, unless Iris kills Misty's bike (if she has a new one)

Yeah, they would get along well! ^^
and back in hoenn i thought that Misty and May are gonna have a quarrell at their first meet but there was nothing like that, not a bit. I was then feeling silly of my stupid imagination hehe x]
So yeah, Misty and Iris would get along well if they meet. Misty seriously is no more cranking like before! but i really miss that x(

Yeah to be honest i didn't xpect Misty and May to get on too xD

Knowing the show, yeah they'd probably get a long. But I have a feeling Iris may not like her at first.