Hi Ashley
I would leave the nest for now. When she loses interest in it for a few days, then you could probably clear it away. If she is actually expecting, the nest need to be intact. If you think it’s in an unsuitable place, you could move it into something like a large shoe box. Typically a rabbit will build the nest about 24hrs before they give birth. They often will stop eating then too. My one experience with this was the rabbit built the nest about 2 days before she gave birth.
If it is a false pregnancy (fingers crossed!) no, this wont hurt her. She will settle down again. The nest building is usually the end of the cycle. The mounting is probably what triggered this. In a false pregnancy they produce hormones like they would in a real one and they dont know the difference. Her body is telling her to prepare for babies.
How long have you had Forrest for? If he was only neutered recently and youve only adopted him recently, then unfortunately there is a chance this is a real pregnancy. Male rabbits can remain virile for a month after castration.
Do check out the Resources tab at top of page because there are some good pages listed on unexpected pregnancies.