R.,
How is your daughter's relationship with these ladies? Are they warm and loving to her? Do they treat her as a "Grandma" should? If they do, and she loves them, then let her feelings toward them be your guide to what they should be called, because the relationship there is between her and them, not you two.
I know that's hard to swallow. I do not speak to my father, and haven't for years. Unfortunately, I have to tolerate him at family events and such, and therefore he does have a relationship with my son. As much as it galls me to admit it, he's good to Mike, and truly loves him. I can't let my feelings about the man taint that, because it is not fair to my son. He will make up his own mind when he's older, but for right now, I just have to go with what is. He calls my father Grandpa, because his cousins do, and there's not much I can do about it.
Family relationships are rough, and rocky ground for a lot of us. The best we can do as parents is try to shield our little ones from the worst of it for as long as we can. If your daughter loves these women, then it doesn't matter what she calls them, because our feelings about the name stem from our feelings about the person. If they aren't good to her, then it still doesn't matter what name she calls them. If your husband is uncomfortable withg his step-mother being called Grandma out of loyalty to his Mom, then go for Nana, or Grandma L, or something that's easy for your daughter to say and remember.
Jess