it is a fairly rare surname
Here is an article although not that up to date I'm afraid, that says it is a fairly common name found throughout Poland, although it is more common in North-East Poland.
polishroots.org/Research/SurnameSearch/DNNArticleArticleView/tabid/353/smid/742/ArticleID/636/reftab/351/t/Misiewicz/Default.aspx
This may be of some use, a list of Misiewicz born between 1850 - 1920 in Podlaskie region:-
geneteka.genealodzy.pl/index.php?rid=B&from_date=1850&to_date=1920&search_lastname=Misiewicz&search_lastname2=&rpp2=50&rpp1=0&bdm=B&w=10pl&op=gt&exac=1
Whether she looks Tatar or not I couldn't say, but you need definite information and facts, not just opinions from posters on this forum.