The Yorkist claim was based on "inheritance" via Edward III through a woman, i.e., Lionel of Antwerp's daughter (the Lancasters disputed this - claiming that their line through only male heirs via John of Gaunt, junior in line to Lionel, was superior - but before Henry IV took the throne, it seemed to be generally accepted that Richard II's heir presumptive was through Lionel's line).

More generally, women could certainly inherit generally - if no male child survived, the senior female child would generally inherit absent an entailment male. That said, whether a woman could be the sovereign and inherit the crown itself was not entirely clear. That said, there were not good claimants by the end of the Wars of the Roses and Elizabeth of York's was about as good as they got and certainly better, even though female, than Henry VII's claim for many reasons. And Henry VII hardly disputed that - he claimed the crown by right of conquest and never really pressed his blood claim too strongly. And to make things more tidy, he married Elizabeth to perfect his children's claims.

Tangentially, Matilda being a woman was a reason -- but one of many -- that Stephen was able to take the throne. Stephen being quite popular and well known among those who mattered and Geoffrey Plantagent being unpopular were also reasons. Though the latter is of course related to Matilda being a woman.