She went to Cambridge.”

Went is the past tense of go.  If you "go to" a school, it usually means you attend there as a student.

She has been to Cambridge.”

Been is the past participle of be.  The sentence literally means that at some point in the past she was at Cambridge, but not necessarilly that she was enrolled as a student.  The usage of the past participle as opposed to the preterite also implies that there is a meaning or reason she was there that is relevant to the present.

She was in Cambridge.”

Was is the past tense of be.  It simply means that she was there is the past.  Also, the use of the preposition "in" means that she was in the town of Cambridge.  If you mean the univerisity, use the preposition "at" instead.  Generally you don't say that you are "in" universities.


To sum up, the verb "to be" in reference to a university means that the subject is simply present at the university.  To indicate that the subject is a present there as a student, one should use "to go to" or "to attend."  The usage of the past participle (be=been, go=gone) in this context (i.e. perfect aspect) indicates a past action with direct relevance to the present.