I suspect she still flees to France since Phillip has liege obligations for Champagne. This doesn't invalidate the betrothal or cause it to be broken.So, my query is Henry married to Jeanne, with Blanche fleeing into Gascony for protection, or Jeanne married to a son of Philip III due to Blanche not thinking Gascony/ England would be safe enough, leading to a massive angry thing, and Henry marrying Jeanne, daughter of Robert of Nevers and Flanders
However, I suspect the Phillip would like to and so we get him inviting Edward over to discuss it. This may lead to Crouchback meeting Blanche earlier and their marriage becomes part of an alternate Treaty of Orleans.