Yes, we all live there together.
This person is no more than a lodger. Depending on the agreement you can give between one week and one months notice for them to leave and they must leave. If they don’t, you can lock them out provided you give them their belongings back. You do not have to get a court order.
There is a useful website which the government have put together which explains exactly the situation for people in your situation.
Here is the link https://www.gov.uk/rent-room-in-your-home/ending-a-letting
Can I clarify anything for you?
We do not really have a specific agreement. She was staying with us as a friend and then begun to contribute to the rent. Does this impact how much notice we need to give?