"Elena's probably the one of that group I've been on the best terms with." She hesitates for a moment before adding. "My brothers used to be here too, both Kol and Niklaus. This was before I got the newer memories" Before she knew how Klaus would betray her and how Kol would hold a stake to her chest -- and then eventually die himself.
"My friend, the one I mentioned before, Quinn, she had been staying with us. Nik had promised me he wouldn't compel her." But the tone Rebekah uses confirms that she's aware of how dumb she was to think he would ever keep that promise -- or any promise, for that matter.
"When I figured it out, Elena was the one who helped me get a hold of vervain to help protect Quinn from it continuing to happen. She helped me protect her."
And the purpose of telling this story is to let Matt know that in her own way, she trusts Elena as well. She doesn't mind that he told her.