Perhaps to her (in paternal line) second cousin once removed, Richard, Duke of York? He would be 10 years older, but considering the different situation arising from a daughter rather than son being Henry V's sole issue, and Richard's potential claim both through his mother and, semi-Salically, his father, one could see Richard being removed from the Earl of Westmoreland's wardship and placed directly in that of John II and III, the new King of England and France and Lord of Ireland. Marriage to his niece would be contra-indicated to begin with, but when some years later it began to look as though no heir would be forthcoming from either John or Humphrey it might have been decided to make the marriage, thus uniting all claims and giving the best chance of an untroubled succession.
It's all a bit of a stretch, I must admit, and there are other candidates that might appeal. Still a thought, though. Another one is a Valois of the Orléans line; there in fact wasn't one of suitable age, because both sons of the first Duke spent decades in English captivity and not in a position to sire children, on their wives at least. That could be amended, or one could be more direct about it and marry the heiress to the heir, to wit Louis XI, who was less than a year younger than Henry VI, and so presumably this daughter that replaces him.
Charles VII probably wouldn't accept his son's eventual rather than his own immediate succession, but such a marriage would have brought assured peace, so maybe. Then we could have a different War of the Roses, with the Duke of York rather than his son as Richard III, as frustration grew at absentee rule and he decided to make himself champion of English independence....