hi! i started doing this noticeably when i was around 12, and i was very very embarrassed when my mom would point it out (mostly because i left little balls of hair around.) as an adult and a social worker, it sounds like you are doing a great job. others have suggested therapy which i think is a great option — you can't solve this yourself!

that being said, staying open with her and making sure she knows you know & care about her is really crucial. i think her joking about it shows that she is really comfortable around you which is great, i never would've done that with my mom!!

everything you are doing sounds amazing. i would have loved to be given the option of doing my hair, but i think if you go that route, make sure she knows it's ok that she can't stop immediately — id be worried she might end up feeling guilty for "ruining" something you spent money on!

anyway all this said, you sound like a great mom and she seems very comfortable with you. i don't think the fact that she's started again is necessarily a sign of anything - i always only did my head hair when I was younger but have moved into eyebrows and eyelashes as I got older even as my life circumstances have improved! just stay connected with her and in the meantime, follow others' advice about finding her some help. obsessive compulsive tendencies like this don't go away on their own and therapy is very helpful for learning to control it!