Seeking advice/help for my sister.

i'm new to here and seeking advice for my younger sister, i'm pretty certain she has a form of aspergers, shes 26 yrs old and its seems to be now affecting her life more and especially her relationship with my other sister, my o/s gets frustrated with her and its causing big fall outs, my younger sister hasnt been diaginosted but i'm sure of it. How can i help my younger sister as she say she feels very lonely and even said she wishes she was dead. my other sister on the other hand probably needs educating on this condition to understand our sister. can anyone help?

also are there any support groups to meet others with aspergers in the somerset/frome area?