It depends on what you mean. English speakers often use "sees" to mean "understand." If the subject of the sentence (she) sees a physical object, you should use "She sees it." If you are using "see" to mean "understand", you shouldn't use "She sees" in this context. This use is ok for first and second person subjects (I or you), but not third person (she). edit: the IPA is /sis/

She sees it. The last s is pronounced like a z. (Seez).

I think it's better to use "sees"