Is it ok for me to ask my mother to masturbate with me?

Don't do it.: No. This would not be appropriate. That is a dangerous lack of boundaries. It would be what is sometimes called 'incestuous'.

No: Even though your are both adults, this is a limit that you will both regret crossing.

You need work: You need to schedule some work with a therapist. How or why you never developed the natural sexual boundaries between family members needs to be explored. It shows courage and confusion to ask & that is something that they can work with.

Dont entertain such thoughts. They are highly inappropriate. If they recur or you cant get rid of them pl see a psychiatrist

A crucial part of healthy development is developing your own identity by learning to separate psychologically from your Mother. This activity could seriously harm your development. Please see a Clinical Psychologist with expertise in multiple types of psychotherapy to help you understand yourself better and how to have a healthy sex life.