When my mare first foaled she was a bit leery of me, and would not put up with anyone else in there by her baby. She wasn't aggressive, no pinned ears, barred teeth, or flying hooves; just would push herself between the baby and I or herd the filly into the corner to hide from everyone. Of course, her filly was so cheeky that it wasn't long before she was glad to get a few seconds of rest.
Be careful of what you do, and always halter the mare up first. I did just in case, as my mother wanted to come flying into my mare's stall and started a crash course in flash photography. I wouldn't handle, or more so take the foal away until the mare is comfortable with you around or the foal gone. It will take a few weeks.
But just because she has a foal, I would not put up with any of her crap. Don't go out of you way to nitpick her, but she does not get to bite, kick, or pin ears at you otherwise, she should not get to now.