You are asking on the patient community, not doctor so it is hard to comment on a prognosis - what are the doctors saying? Did you ask?
Are they planning to remove the lesion? She is pretty young to have had a stroke - what was the cause - do they know? I would guess the stroke caused some issues as that normally causes weakness and all.
The medication she is on is to prevent seizures. So until they remove the tumor, I would guess that she would need the medication until the tumor is resolved.
I would get more information from her doctors.
A meningioma is a (generally) slow growing tumor on the meninges, or lining of the brain. People with brain tumors often suffer from seizures as the tumor grows and presses on the brain. It is not uncommon to be on medications to help with the seizures. Some people need to be on them for the rest of their lives, while others can stop them after the tumor is removed. There are several different medications available, and it may take a while to get the right med at the dose that works for her. If her seizures are increasing, she should contact her neurologist and discuss this with him/her.
Treatment of meningiomas varies, depending on size, location, and what it is pressing on. Doctors often advise waiting and watching, since they are slow-growing. However, if the tumor begins to effect a person as it is effecting your mother, surgery or other treatments are often considered. While these tumors are generally slow-growing, they can have "growth spurts" during which they grow rapidly. This can explain a sudden increase in symptoms. These growth spurts are often linked to hormones, so if your mother is approaching menopause of taking hormones of any type, this can cause rapid growth.
Waiting and watching is common, however given that your mother's symptoms are severe enough to affect her life I am surprised that they allowed over a year to elapse between MRI's. Meningiomas are often watched more closely when first discovered to see what it is doing. A sudden increase in symptoms will often warrant an MRI sooner than originally planned. Is she consulting her neurologist often? Has she had a consultation with a neurosurgeon? If she has had a consultation with a neurosurgeon, has she gotten at least a second opinion from another doctor?