While I am not one who normally encourages full-time learning, except for yechidei segula, I think if there was an agreement here, she may be required to honor it.
There is a mishna which states that if a girl promises a certain dowry to her chosson, and she goes back on it (pashta lo es haregel), then she may remain an agunah for the rest of her life (teishev ad shetalbin rosha). In other words, he need not marry or divorce her, but leave her in limbo (kiddushin but no nesuin). However the Rambam says that if the promise was made by the girl, then this applies. However, if the promise was made by her father, and he dies, then she can say, what can I do, I tried my best. Either marry me or divorce me so I can marry somebody else.
It seem that if the situation changes, like the boy was receiving a certain kollel income, but he no longer is, and they are starving, then he must reassess and possibly make up for the money in some way or another. But if the circumstances have not changed, and the girl just wants a higher standard of living, then she may not be entitled to it, if she promised to live on the lower income, which continues.
Just my thoughts. Of course if she absolutely can’t take it, then maybe she should divorce, but that would be a tragedy for the child.
The moral of the story is that people must not make deals before they understand all the ramifications and are sure they can keep them. This is true of buying a house or car as well. One can’t decide a few months later that he wanted a blue car instead of red, and now wants to skip the payments.
Anyway, here, the best advice may be Ann Lander’s sage wisdom, are you better off with him or without him?