A few suggestions:

1. The past cannot be undone nor returned.

2. Focus on the memories as positives that would lead you in the future.

3. Rationalise what she might want you to do in your new phase in life ... to live with sad memories or fond memories.

4. As hard as it would be ... a person needs to let go of the past and move forward. It is like this, if a person is holding on to the past with both hands, what would he/she had to pull/propel them forward.

5. When one door closes, there is very little gains/merits to try to enter that room again. There are many other opportunities to explore with the past memories are guiding lights.

6. The mind should prevail over matter.

There are no set solutions to these unfortunate situations, for each would take his/her path based on personal optics plus integrating suggestions from others.