Elektra never said anything because of past rejection.
Rejection from girls. Rejection from her family. Rejection from society.
So she distanced herself from people, in fear of rejection.
Then Faith turned up, kind and secretive, and distanced.
Then Faith started to open up, and the two girls started to get closer. They became friends.
Elektra was going to tell her, but then Mike told her she was being transferred to a new home and the next day she was driven away from The Dumping Ground, regretting that she never told Faith the truth.
That she was in love with her.