manga said: "When he learned of his tribe's mortality, I hoped he would choose, by my aid, to defy fate." She's referring to events in book 3, during the Original Quest. So she has known at least that long that she can remove Wolfblood.
Yes- I guess you are right... that would suggest that she asked Cutter if she could remove his wolfblood in Book 3.
Hm. Why didn't she ask him before, I wonder? Was she really never going to tell him if Winnowil didn't? Keeping that information secret makes sense if she thought there was nothing she could do about it- and that knowing could only upset him. But if she knew she could have offered him the alternative of immortality... why not tell him? And why not tell him and offer this right away- instead of being so freaked about about the recognition?
I personally think that, you do have a point- she must have suspected this was possible.. but that one of two things happened. Either she asked Cutter right away after Winnowil told him- and he told her no, and to keep it secret from the rest of the tribe. Or... She wasn't sure she could do it until Winnowil did it to Windkin. And her offer came after that.
I think... I think it's the latter. Winnowil said that "had he [Windkin] not been a product of Tyldak's wholesome seed, he would not have survived the work I have done on him." It doesn't seem, at that point, that Winnowil thought full Wolfriders could be changed. If Winnowil didn't think it was possible- why would Leetah?
Unless that was just Winnowil's racism talking...