1) Always keep copies of everything you ever submit to USCIS
2) If she doesn't remember the dates exactly she needs to reconstruct it based on emails, messages, phone geolocation history, asking family, contacting previous landlors, searching through paperwork.
3) She must remember all of this information. In case there is interview, she may be asked to tell dates and places on the spot.
4) Making information up is not a good idea. USCIS can use this as a weapon to accuse her of misrep (unlikely but possible)