Everytime they talked; she knew.
Everytime they laughed at something, anything; she knew.
Everytime they had a disagreement and later made up; she knew.
She knew that they'd leave, like all others before them, because she couldn't give them what they deserve that is, someone better.
She knew she was too less for them.
She knew she couldn't give them the whole of herself.
She just couldn't.