Pretty much everyone I have spoken to about this discernment has asked "How do you know?" All I can say is, during my time there, I truly heard the call of Christ to come before Him, asking me to return all that I am, and all that I have been given, to Him as a free gift and loving sacrifice, or to choose to return to the blessed life I have been leading. My heart leapt, and with both solemnity and joy I said "yes!"
Please go read the rest of post - it will be well worth your time. Have you ever wondered what kind of woman enters a cloister, or why? Mary may have some of those answers for you.
Mary has a great deal of college debt to erase before she can enter on June 11, so if you are a person of means and find supporting Vocations (especially during Lent!) to be a worthwhile cause, I urge you to do what you can.
Please keep her and her intentions in your prayers.