M.A Psychology

You have not written about the college name where you wish to do the M.A. Psychology. However the eligibility criteria of Delhi University is given below for reference please. Eligibility criteria of M.A. Psychology of DU B.A. (Hos. ). / B.A. (Pass) /B.A. Programme Examination in Psychology of Delhi University and other Universities recognised by Delhi University with 55% marks or above in Psychology and 55% marks in aggregate
2. Graduation from Delhi University or other Universities recognised by Delhi University with 60% of marks or above. So from above you are eligible for M.A. Psychology course.

Yes, if you have made your mind to change your stream from commerce to psychology, you can go for that. But for this you must have cleared your bachelor's degree i.e.( B. Com) with an aggregate of 50% marks. During your M. A. (Psychology) you will go through core courses, electives ,and practical courses.