Random Pet Peeves

There are certain things that just get under my skin and I really can't help it.
One of those things is really bad grammar.
I hate it when adults use bad grammar to speak to their kids as if that's some sort of baby talk or something (I don't really like baby talk much either, but that's another story). I realize that kids are going to make some grammatical mistakes as they are learning to speak and that's okay, even sometimes cute, especially when it's your own kids. But, there comes a time when I think kids are old enough to speak somewhat correctly.
For example, the kids that live in our basement both make the same grammatical errors and I'm sure it's probably not their faults. But, I still can't get past it. They both use "her" instead of "she" and it just makes my skin crawl. For example, they say things like "Her's asleep", "No, her's not", "Her wants to do it", etc. And it's not just once in a while, I don't think I've ever heard them say "she" at all. And they are 6 and 3--not really little kids anymore. I think I could probably get past it, except that they are at my house playing almost everyday. And the other day, Haley started using "her" in the same way they do and she never once did that before they lived downstairs. When it starts rubbing off on my kids, that bothers me even more. I wish it didn't bug me so much, but I honestly think it makes me like them less which just makes me sound so mean and shallow. I guess I'll have to work on that one.