Difference between the following:
A) When does she go to office?
B) At what time, she goes to office?
C) When is she going to office?
Difference between the following:
A) When does she go to office?
B) At what time, she goes to office?
C) When is she going to office?
Version A) implies recurrence. You might as well have asked, "When does she typically go to the office?"
Version B) is grammatically incorrect, but could be adjusted to read as follows: "At what time does she go to the office?" In that case, the implied meaning is identical to version A.
Version C) also needs a slight adjustment: "When is she going to the office?" This version implies that you are inquiring about a specific occurrence, or even that you are waiting on the event to happen.
EDIT: As macserv stated, the second question is incorrect. I haven't seen that coming, sorry :)