All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
If this girl is pious and of good character then her not putting on Niqab should not have an impact on your decision. In fact, there is a difference of opinion among the scholars over the issue of Niqab whether or not it is obligatory, and each has his own evidence.
So, it is a controversial issue. We are of the opinion that covering the face is obligatory and you can try to convince her or oblige her to put it on after you get married with her.
For more benefit on the obligation on women to wear Niqaab, please refer to Fataawa 196833, 326989, 83723, 81554, 369070, ’s wives">115107, and 83033.
Allah knows best.