According to Minchas Yaakov 112:2 and Darchei Teshuva 112:94, one who is always careful with Pas Yisrael and now wants to start eating Pas Paltar would have to be Matir Neder. Suppose a girl who was always careful to eat Pas Yisrael is now marrying a guy who eats Pas Paltar, would she still have to be Matir Neder or, since she is changing her status by marriage, is it not necessary?
This question is applicable by any case where the wife maintains a Chumra which the husband does not. The above is an example.