My mom was diagnosed with rp 20 years ago and is now slowly losing her vision. Is there any cure for rp now? If not, what can she do to help.

Not at this time. The most promising work in the field of retinitis pigmentosa has come in the area of genetics. There are no current therapies available at this time other than limited help with vitamin a and lutein. She can help by enrolling in one of the genetics studies if available in her area and identifying other family members to participate in the studies.
Treatment on the way. As of now very minimal help from treatments including high dose vitamin a (berson study) and leutin. Recent studies show that some genetic subtypes are sensitive to these treatments, others more resistant. See wpost 1/24/12 on results published from ucla on possible use of stem cell injections for blindness from macula degeneration. There may be light at the end of this tunnel.