Gosh, this is hard, so hard, but so hard....
It sounds puerile and trivial to say that if you Love her the best you can do for her is to let her go.... But it's true...
However, she deserves to know that you do not let go willingly....That it is painful, and that you have feelings for her that cannot simply be erased, forgotten and discarded....She must expectand understand that you will undoubtledly be travelling a roller-coaster of emotion for a while yet.
Try to separate the Practical from the Emotional...do not confuse and merge the two, neither resort to using one to underpin or evaluate the other....
Do not keep yourself to yourself, but seek the help of those close to you to help carry the burden. It will become lighter.
Hard but true to realise and come to terms with, is the Truth that many have trodden this path before you. It is a familiar one, believe me....
Please know, dark and painful as things currently are, one thing is undeniable:
This too, shall pass......