Why does my cat hide under my coffee table and scraches anyone who comes near her reach?

You cat's behaviour shows a high level of stress and poor socialisation. If she is hiding when every is up and only coming out at night when everyone is in bed you need to work out what is scaring her so much.

Is it a new thing or is she young and has been doing it all the time?

Use treats as a way to wield her out, don't force her just leave them out of the floor and perhaps call her, sit at her level aswell rather than standing up. She sounds nervy or scared of something. You can praise her when she comes out on her own terms. If you keep doing that chances are she'll eventually feel a lot more comfortable and come out to play instead. If she trusts you, you can show her who's a "safe" person. It won't be a quick thing but very slowly you'll watch her grow in confidence until she feels safe enough to come out from there.

I have a very skittish cat myself, she hides whenever new people are about and hid under the table when we first got her. She eventually learnt to trust me but I still have to call her over now and again and show her who's ok to trust. She is very frightened of men but she is fine with my boyfriend now. To show her you can literally just call her over and get the person to pet her at the same time as you do. Cats may not show love like dogs do but they do have their favourite person who they trust.

Get a cat tree and put it near a window. Your cat needs its own space. Get one with the box in the bottom level so he can decompress.

Also, play with your cat twice daily with a feather on a stick for 15 minutes. It uses up that energy, soo friends wool draw him out with it and hell be well socialized and happy.

Most cats are nocturnal [come awake at night]. She dabs at people going past because it's a form of play.

Your cat feels stress. Get her some catnip to mellow her out.

he goes under the table to masturbate leave him alone!!!