"Oh. I'm happy for the two of you." She heard Tyra said to both of them.
"Thanks." She replied hesitantly, suddenly feeling mortified for what she just did.
When she saw the defeated look on Tyra's face, she realized that Tyra was genuinely hurt by her action. Tyra must have real feelings for Alex and she just crushed it with her lie. She felt such a horrible person for purposely hurting another person.
Then, it came to her attention what her actions signified. She just confirmed to Alex that she was agreeing to the contract by acting as his girlfriend in front of her ex. She might not have signed the contract yet, but she was already bound by her honor when she started playing the part tonight.
On the other hand, Alex took this as an opportunity to get what he wanted. A card that he could use against Dani and a way to ward of Tyra's advances. Everything was falling into place and he could not be happier.