I would he happy to help assist you in understanding your dream. Through what I believe your mother's dream is saying is along the lines of being symbolic. Snakes can be representation of fears in dreams,. Things she maybe "afraid" to deal with. Often times relating to the things of our flesh. Sins, or things that can overcome us, addictions, anger, etc.. With your mom dreaming of falling asleep with her deceased Mother can be showing guidance in her life to take a "deeper" look spiritually into what her mother is showing her. The snake having bit here repeatedly is showing how her deceased mom is showing things to your mother that she had perhaps had to deal with in real life and or did not actually address these fears of and it may possibly relate to her death. So the dream is a guidance dream. I hope this has helped. If you have any more questions feel free to ask.