Recovery can take up to a couple of years.
I wish your mother a speedy and full recovery.
http://www.ninds.nih.gov/disorders/gbs/detail_gbs.htm
I'm so sorry to hear abuot your mom and I know you are worried about her. According to the above link, recovery can take from a few months to years. The most important thing is keeping her limbs flexible (moving them for her) and then as she gains her strength, rehabilitation (physical therapy) will be able to assist her as well.
I think it would be best for you to contact her physician about the pain she is in, because she may need a prescription to help her through this part of the illness. I believe the pain she is experiencing may be due to the nerve damage, and as the nerve sensations return they can increase the pain until they stabilize.
I pray that she will begin feeling better soon. I know this is hard to watch and she is so fortunate to have you loving her and caring for her.