If the rumours about Richard I are true (which I am doubtful of) then her marrying him changes little. Either way, the marriage probably doesn't butterfly his involvement in the Crusades, so he would spend much of their marriage away, and not producing heirs. Then again, it's not impossible that whatever issue Richard had with Berengaria of Navarre that kept him from staying with her during their marriage isn't an issue he has with Douce II of Provence, so it's not impossible they have a more successful marriage, and he produces an heir.
I don't see much difference to OTL arising from her marrying John, either. If John really wants a war, then he can try and press his wife's claim to Provence, but that seems pretty suicidal. Obviously the pair will have different children to those born in our timeline, but it's difficult to see how different they might be in this timeline. I don't foresee an Angevin Occitania arising as a result.