Ending a relationship through text is kinda sad. It is avoiding confrontation aka not being a social person and hiding your true feelings.
She has been very kind to you, but that doesn't mean she can expect every guy to stay with her forever because she offered help. Life always changes and so does your view on things. You need to clarify to her that you have other goals in mind right now and she is not to blame for that. Be completely honest and tell you will always love her and she has a place in your heart. You can even stay in touch and help eachother our as friends if you feel like it to show your appreciation.
Telling her that "you'll always love her" is like giving her false hope for getting back together. Plus, that line is so cliché and cheesy.
There goes my last fuck