Yes, it is scientifically possible. Though a third party (male sperm donor) is still required. Scientists working for a British biotechnology company, as well as doctors at Oregon Health and Sciences University have been working on complex procedures but are fighting the ethical red tape and are not currently using the techniques on patients.
This is the basics of the procedure being used by the doctors in Britain "The nuclei from the father's sperm and the mother's egg, which contain the parents' DNA, were removed. The nuclei were put into another egg from which the nucleus had been removed, but which retained its mitochondria. This new embryo contained the genes from both parents plus a tiny amount of mitochondrial DNA from the donor egg."
The scientists in Oregon have a similar yet slightly different approach with procedure explained as "Doctors would remove the nucleus DNA from the donor eggs and replace it with nucleus DNA from the patient's eggs. So, they would end up with eggs that have the prospective mother's nucleus DNA, but the donor's healthy mitochondrial DNA."
This approach can easily be modified to fit a lesbian couples desire to have a child that is related to both of them. Scientifically it is possible for two mothers to be directly related to a child, but the sperm is still a relevant part of the equation. It is not possible, so far, to create a functioning embryo without male sperm.
And my reproductive biology book and studies: Trends in Endocrinology and Metabolism by Claire Bourgain.