There is nothing inherently wrong with a female rabbit allowing a male to mate with her. Rabbits are polygamous animals, meaning they can have multiple partners. When a female rabbit is in heat, she will instinctively seek out a mate. If a male is present, she will allow him to mate with her. This is a natural process and is essential for the continuation of the rabbit species.
However, it is important to note that rabbits can reproduce very quickly. A single pair of rabbits can produce up to 50 offspring in a single year. If you do not want your rabbits to reproduce, it is crucial to separate the males from the females. You can also have your rabbits spayed or neutered, which will prevent them from reproducing altogether.