False pregnancy?

Hello there! I’m a new bunny mum! Almost one week before a friend of mine gifted me one female rabbit of his. Note that she is unspayed. We’re doing all well until 3 days ago, when she went into her cage (she roams freely in my house but I have her cage open to rest whenever she wants) and started digging in the corners, gathering hay with her mouth. The day after and all night she was pulling out fur from her belly and it was obvious that she was building a nest. I provided her a nest box and she transferred the nest inside. called my friend immediately and said to me that a couple of weeks before handing me the rabbit one of the male rabbits went in females’ hutch accidentally. He saw him breed with Muffin (my rabbit) but he interrupted them thinking that she couldn’t get pregnant.
The nestbuilding finished yesterday morning but no signs of babies yet. So here comes the question, is she pregnant or she thinks she is because of the unsuccessful breeding? Can a rabbit get pregnant if breeding is interrupted?
What I’m thinking is if they bred more before my friend noticed them. If so, she could be pregnant. How do I know? I’ve read in some sites that from the time she pulls fur she gives birth in a day. So I’m concerned because no signs of birth behavior yet.

There isn't anything to do than to wait the full 4 weeks to be sure. It can differ when does pluck fur, so this isn't a real indicator. Just take care that she doesn't build a second nest somewhere in the house.

Signs that she's about to kindle can be a slightly reduced appetite, 1-2 days before, and getting tired more quickly, but at times I don't notice anything.
If you notice that she goes into labour check on her regularily, but without disturbing her, just to make sure there are no kits outside of the nest when she's done.

I have a rabbit that nests a week before kindling, another gave birth on day 42, so don't stress over anything. Just make sure she has everything if she would kindle. If it would be her first litter, don't expect much anyway. I'd advise maybe having a vet feel her for kits. Heads up, rabbits get diarrhea close to they birth. Feel for kicking. If she is pregnant, you might be able to see it. A false pregnancy isn't much to deal with either so don't stress over anything and just take it one day at a time.