Anna wanted to strangle her friends for revealing unnecessary information to Lexus. She was young and childish then and had bragged to her friends when they kept consoling her about her breakup with her first boyfriend.
That guy was his first love and her first heartbreak so Anna cried about him a lot. He was her boyfriend since she was sixteen and she thought that he was patiently waiting for her to be ready since that was what he told her.
She didn't expect that he was actually two-timing her to satisfy his desires. If he had clearly stated that it was difficult for him, she would have done it with him earlier. But instead, he went and cheated on her.
He kept apologizing for cheating on her and kept saying that she was the one he loved and he would never do it again, but Anna was already disappointed in him. And she had also gone past the point of no return. She slept with Lexus that night out of spite and anger.