A "pseudo mother" ? A step-mother? Those are incredibly insulting as well as inaccurate terms.
I can only assume that you're using them through either ignorance or homophobia or both.
I don't think you'd refer to a father whose partner had conceived using donor sperm as a "pseudo father" or a stepfather, would you?
As I said in my earlier post, there's a BIG difference between a partner of a parent who arrives on the scene after the relationship of that child's parents breaks down (a step-parent) and a non-biological parent who is in a relationship with the biological parent when their shared child is planned, conceived, born and raised. They are a parent. Nothing "step" or "pseudo" about it.
Also, why assume that the child of lesbian parents would have no male role models in their life? What about grandfathers, uncles, family friends etc? Just because lesbians don't tend to have sex with men doesn't mean they don't know, like and in some cases even live with them!
I really do think this is a sad case, and the problem is probably caused by the fact that there wasn't clear enough communication between the various parties about what the extent of the donor's involvement in the child's life would be.
But I know that if, say, a friend of ours had donated their sperm so that DH and I could have a baby, and then demanded to take that baby away from us for the weekend, we would be fucking horrified. And I very much doubt that DH and I would be vilified for not wanting to "share" our child in this way. I very much doubt that DH would be referred to as a "pseudo father" or accused of not putting the interests of our child first.