My bf’s mum gave me a laptop but now wants it back.

Location: England. I started university in September and my bf's mum gave me a laptop to use. It was originally bought for his younger siblings for homework, they never used it, and then later his younger sister tried to download games on it but found it ran them really slowly, so again it wasn’t used. The conversation went something like her asking me what i was planning to use for university. I told her I would get a pen, and paper, or buy myself a laptop, but she said I could have the one she had bought as it wasnt in use. 9 months later and I no longer speak to her, blocked etc. My bf and I are still in a relationship but I had some issue with his family that led to this outcome. She recently asked for him to get the laptop back. He discussed it with me and agreed that I was never told that I needed to give it back, and therefore assumed that it was mine to keep. I dont have the money to replace it, otherwise this wouldnt be an issue and I’d give it back. She is saying that she bought it for his younger sister to use for school work, and since she now needs it, if she can have it back. We have responsed no, with the fact that it was given to me and I was never told I’d have to give it back.