Does my son's grandmother have a chance at getting custody (CA)

Hello everyone!

So for a bit of background, I am a single mother with full physical and legal custody of my 10 year old son, who both used to live with my parents. However, in 2022, my mother kicked me out because we have a very rocky relationship, but my son stayed with her because I had active addiction issues at the time and knew my parents could provide a more stable home.

I moved back to the area in 2023, and checked myself into rehab at the beginning of 2024. I completed rehab, moved into a sober living environment, and reenrolled in school. Since moving back, I have been financially supporting my son, and while he has remained living with my parents, I spend 5 days a week there caring for him.

My life has greatly improved, I'm stable, sober, and due to graduate in the spring. However, I currently rent a single bedroom and cannot afford a place we will both be allowed to reside until I graduate and start working.

Yesterday, my mother told me she is filing for custody. What are the chances she will win considering the current circumstances?

Thanks for any input.

ETA: corrected dates