mom cat suddenly aggressive toward kittens

I figured my mother cat would probably start weaning her kittens soon, but I cannot believe the change that has come over her in a single day. Yesterday she was letting them all nurse without complaint, and today she is attacking them if they even come close to her. Her being extremely angry all day and keeping her tail violently wagging doesn't help matters much with playful kittens! She has been meowing NONSTOP all day long. I was amazed at how well behaved she was when I took her in, but today I feel like I have a different cat.

She stares out the window meowing loudly and makes a dash to escape everytime I open the door. She climbs my curtains and jumps on my desk and shelves, knocking things over. She NEVER did any of this before. She has always been very calm and never seemed to mind not going outside the least bit. She was never much of a lap cat, but now she will sit on my lap when I'm at the desk and attack any kitten that comes close to me.

I've never had a cat that had kittens before. Is this normal? Could she just be having a bad day and calm down later, or do I need to separate her from the kittens? I don't have a lot of options here... I'm staying with family right now and they own three cats that she doesn't get along with at all. The only place I can put her other than my room is in my family's camper. Would this be advisable until I can find homes for her and the kittens?

If the kittens are eating on their own, please get mom spayed quickly. That will calm her down, but yes, it is normal. She has done her job as a good mom, and she will growl, bite and hiss to drive them off her. It is just their way and how they survive. Give her about 2 hours away from them by either putting them in a different room, or her. Bring in a cat condo, or clear off a shelf where she can get up and out of the way when she wants to.