I think her coming in like she owns the place is just part of a larger issue here. She clearly feels like she's "the boss" of you. I don't mean that you're the boss, but it is a partnership. NO MORE ten minutes early and 1hr and 10 min late! I know you said she's only 10 min late, but if she is supposed to be here at 4 and shows up at 5:10, she is over an HOUR late. It's time to nip this in the bud.
I also don't like it when parents wander in. I do understand the desire to see where the child is spending it's day. But I hate feeling like I am caught off guard by a parent walking up behind me or something! I also pee with the door open and would be mortified if someone came in at that exact moment!! LoL
Not to mention, although I tidy up after all the kids are gone, the end of the day can look like a bit of a disaster has occurred. Toys strewn about, dishes in the sink. You know....
I am actually going this weekend to pick up an intercom/doorbell system to remedy this problem!