Marriage in such a situation is a bad idea. It is not easy to divorce, especially if there is a kid involved.
U claim there is personality mismatch. I doubt this happened only after discovery of pregnancy. Clearly, the both of u are not compatible from the start, and any marriage is unlikely to succeed. Perhaps u are better off with another woman, perhaps she is better off with another guy. Why enter marriage when there could be better options.
6 months with "personality mismatch" and u got her pregnant. Things don't happen by accident, and most cases are simply instances of recklessness by not using protection. Lets be real, not using protection is a delibrate attempt at impregnation. She wants ROM and u are now here asking if that is the right thing to do??? If u love her, u won't even be asking this question. U will face all challenges together with her, regardless, unconditionally.
The best solution now, is to do wad u wanna do, and let her do wad she wanna do.
Forget about marriage and any legal relationship. But at least help out in every possible way. This may sound so screwed up.. but the fact of the matter is, u gambled and u lost.