Only child with absent father feels lack of family

[Biglaugh]

My daughter is constantly sad about being the only child. She did have my brother and my mum until she was three but they both died within a short time.
Her dad has always been absent. He does have various children around I think (he was a musician) but they will be considerably older and I have no idea where they are.
So I am the only immediate family she has and she feels frightened of it just being me. I have cousins and I have done all I can to involve us in their lives but they are older than her (she is now 18) and so there is a gap.
I don't know what to do to make her feel better. Anyone in similar boat?

She is 18 ?
Encourage her to speak to a counsellor and do some cbt to combat the anxiety
A counsellor could help her get more confidence and develop her own networks

That's a good idea. Thank ypu