Whats the best thing i can tell this girl?

this girl i went out with, named elizabeth. she was the best thing that has happened to me in forever and i let her go for the most retarded reasons, shes seeing someone else and im happy for her but i miss her and she knows i do and i get the feeling she misses me too at times when we talk, i just want her to know i still care about her allot and i miss her too what can i tell her?? everyday i think of the perfect text to send her but i lose my thoughts as soon as i start typing, i just want to say the perfect thing to the perfect girl. you know?