I actually think they do not really resemble GW sisters all that much, beyond being female space knights. The helmets, shoulder pads and legs are not power armour copies (maybe the weapons and backpack too, I cannot see them too closely), certainly much less than many 3rd party stuff. I guess most sisters of battle players are probably more open minded than your average GW fan, and so this stuff certainly passes as sisters of battle, but I would find it much easier to use these in some other setting than most 3rd party not-space marines.
Anyway, they are lovely and I am tempted by a squad even though I would have no use for them whatsoever.