What is the choice for a sister who is late for nikah?

Should she ask to marry a married man or a man who is younger and has lower Western education than her, though the Islam is okay, or should she wait till she gets a single man that is older and has higher education than her?

She should marry early as the Prophet (sallallaahu alaihi wa sallam) advised:

"O young people! Whoever among you can marry, should marry, because it helps him lower his gaze and guard his modesty..." [1]

Being single is not important, neither is education, as long as the person is well educated in Islam and has good Islamic manners. “Okay” is not enough, if his modern education is less. Also considerations of financial capability of looking after her should be important in both cases.

Reference:

[1]  Sahih al-Bukhari: 5066