@Marianne199 Do you have a private room? Sharing an open area for sleeping with the host with little to no privacy? If you have a private bedroom, you can't dictate who the host allows to stay in her home, a boyfriend, a friend or family member, etc. If you are in a shared space for sleeping, then you have a case for a cancellation and request airbnb to rehouse you (and no, you don't get to ask for a refund for the time you have already stayed) if the host stated in the listing description or messages that you would be sharing the space with her only.
I wonder why you say your name is Mattéo, but your profile says Marianne?