Consider admitting her in a hospital.  Once she is better, she can be started on a long acting injection.

Admit her in hospital..Then u can start long acting Medication and injection

You need to meet a psychiatrist with all her past treatment records and if possible with your mother. There are 2 options available in such cases - 1. She needs Hospitalization for few days after which she will take medication at home. 2. You may give her medication by mixing in food items, there are mediation available which are tasteless and colorless. All the best