I am a social worker with geriatric and medical social work experience and a stroke survivor myself. There are no clear cut answers for how long you should wait. It sounds like she currently needs 24 hour care and I'm glad you have that set up. If it was my mother I would provide that care until she gets better or until caregivers are unable to assist any longer because individuals tend to do better in their own homes with assistance. Also, there is no way to judge if or when her memory will improve. I had my stroke 3 years ago at age 43 and still have some memory problems, but some recover quickly and others never do. There's also another good website with great information and support: strokenetwork.org They won't be able to give you any idea if or when she will improve but you'll most likely get a lot of people to respond to a post with a lot of different backgrounds and experience that might help.
Pam