It should be fine. When the students apply to college here in US, they usually have to wait a month before they get I20 back to nepal, again they have to schedule the interview which takes upto 2 -3 weeks. Based on that assumption you should be fine. 
Another important factor for your mother's visa are the ties in Nepal. She needs to show that she is needed in Nepal and will return back (assuming you are a student) and not a gc holded or a PR.