Lesbianism is Haram (prohibited), and is a major sin because it is an act that contradicts the Ayahs (Qur'anic verses):
And those who guard their chastity (i.e. private parts, from illegal sexual acts)
Except from their wives or (the slaves) that their right hands possess, - for then, they are free from blame;
But whoever seeks beyond that, then those are the transgressors;
masturbation is Haram because of the above-mentioned Ayahs and due to the harm it causes. May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.