The reason why she did not call and went out directly was because she wanted to walk around. She had eaten a little too much that night and had to take a walk.
She kept telling herself that she had no feelings for Finn at all.
A few minutes later, there was a knock on the door. Monica knew it was Finn, but she did not open it. Then, the phone rang after a while, and she did not pick it up either.
Finn sounded a little agitated as he stood outside the door. "Monica, if you don't open the door, I'll kick it down."
He was probably afraid that something had happened to her.
Monica believed Finn meant what he said, so after some thought, she opened the door for him. As soon as she opened the door, she saw the panic on Finn's face.
When he saw Monica standing in front of him, he calmed down a little. "Were you taking a shower?"
Monica did not answer him.