My 85 year old mother has been living with me for 8 months, do I have a chance at filing for guardianship of her?

If her doctor will give a letter stating her mental incompetence, you could proceed with filing for guardianship. If there is money for attorney's fees, this would be the way to go, to hire a lawyer to help with the guardianship. If you want/need to save money, in my area there is free help available to fill out the forms and file the papers for a pro se guardianship hearing and there may be similar programs in your area which would give you the option to do a pro se guardianship.