17 year old daughter has imaginary friends

This is the most recent thing she’s told me. She struggles badly with OCD and anxiety and her mental health hasn’t been very good recently. She came to me and spoke to me about it and told me that she has ‘borderline’ imaginary friends and often feels ‘stuck between worlds’. She says she talks to these people that have names like there real. She’s always been very imaginative, creative, she writes a lot. I asked her how long this has been going on for and she says she can’t imagine her life without them.

I’m a bit concerned. It’s all fine but I don’t know if I should be worried about this? If I should mention it to her doctor? Imaginary friends are fine to have but at 17? She turns 18 in a month.