My mother is balding

I want to help her and buy her a derma roller at the least but how do I have that conversation with her without destroying her self esteem

She should see a doctor. Female hair loss is very different than male hair loss as there are many common conditions and this could be a sign of some important change in her overall health or some disease of the hair and scalp more common in women then men.  Dermarolling is not the answer for most women unless they have genetic balding and female patterned hair loss.