Move to Marie Leczinska? 

Since English language obviously doesn't have its own name for this woman (Mary Leszczyńska?), Anglophone historians have to choose between Polish spelling - Maria Leszczyńska - and French spelling - Marie Leczinska. French language was, and still is, naturally closer to English than Polish, which is probably why most Anglophone historians choose Marie Leczinska. A quick Google Book Search confirms this: Maria Leszczyńska gets 96 "English-language" results (though all I've seen are Polish books), while Marie Leczinska gets 808 English-langauge results.

Besides being closer to an Anglophone (for whom the article is written), the proposed title has another benefit: the lack of diacritics. "Diacritics, especially Polish diacritics, make articles much more difficult to link to (it takes me about a minute to track down the proper letter and then copy/paste it), they interfere with proper alphabetization in category listings, are visually very intimidating to many English-speakers, cause confusion for pronounciation, and do not always display correctly on all web browsers."

Another posibility is Marie Leszczyńska; it is significantly more popular than Maria Leszczyńska (c. 400 hits), but Marie Leczinska is twice as popular as Marie Leszczyńska. Moreover, Marie Leszczyńska lacks the aforesaid benefit: it contains diacritics.

That being said, I informally propose moving the article to Marie Leczinska.