If a woman gets married to a man who davens Nusach Ashkenaz but with modern hebrew pronounciation, will she have to switch from her Ashkanazi pronounciation to his hebrew one?

Normally the wife takes on her self the customs of her husband. If it is a simple task, like eating Kitniyot on Pesach – she must follow his custom. If taking his custom will prevent her from having proper Kavanah in her Tefilah like might be in this case – she can keep using her old pronunciation.