I do think she is better than him, but not that much better. With that said even if she was A LOT better than him, there is still the reality that she has to find a better partner than him, or else she's just going to be in the same situation, but worse- she'll still be better than her partner, who is worse than Diaz was. I honestly do not see that any of the known potential partners for her is better than Diaz. At all.
Now of course this doesn't take into account interpersonal relations, which it does sound like may have deteriorated, and I agree with others that if that had gone past a point of no return, that's enough reason to want to leave a partnership. But if her main issue and what lead to the deterioration is that he's not as good as her, unless she knows something we don't I'm afraid she's about to get more of the same with her new partner.
I do suppose it is possible she is thinking of country-hopping, but while don't think they'd take it to French levels, I highly doubt Spain would easily release her, and she's going to be 23 in less than 2 weeks. Waiting a year or two for a release can't be a good prospect.