2 non Jewish women in lesbian relationship is frowned upon by the torah in the strongest terms, we learn out the prohibition of lesbianism from the disgusting ways of Egypt, furthermore the medrish says lesbian “marriages” were one of the cause of the mabul.
So even if it were not technically forbidden it’s still clear from the Torah it’s evil! In fact by the 7 mitvos there is much room to say that some actions that are not included are even worse than those that are. We know this from the fact that god gave a special dispensation for Kayin to marry his sister even though the world could have been populated through adam and his daughter that would according to the the tanaim we pasken like not have violated any halachas,but would have been worse haskaficly, so god gave a special suspension of the issur of a sister for kayan, so adam would not have married his daughter who was mitur al pi halacha to him