Another aspect of the new and old friendships explored this season in "Crazy Ex-Girlfriend" is that it allowed the characters to grow in new ways. Darryl figured out how to bond with Nathaniel. In Sunil, Paula found someone who saw how much of a helper she was in some of her other relationships. Heather, Valencia, and Rebecca bonded as single women. But one thing that happens often in media, is that our character shows some growth and then the universe immediately rewards them. Now in fiction this is kind of a shortcut, the uncaring hero rescues a cat and we all know that he isn't as uncaring as we thought. The selfish heroine does something selfless, and we all see that she is grown. Most audience members know that this is a storytelling shortcut, helping one person across the street does not earn you a job promotion.
But, of course, Rebecca is not your average audience member. So, she saw that when Paula's trip was in jeopardy now that she had kicked Scott out, Rebecca, swept in and decided to babysit for a weekend, despite her lack of experience. And she was doing pretty well, until she had to stalk Josh. But even though Tommy was okay and home, Rebecca owned up to misplacing him and turned Josh away in favor of staying to help Paula when Josh realized that Rebecca was the soup fairy who had always cared about him.
Now, Paula has always been biased about Josh, so she encouraged Rebecca to go after him.
Love isn't a prize you get for being unselfish. One of the things that Rebecca and Josh have struggled with is that they are looking for signs instead of looking within themselves. Josh decided Rebecca being his soup fairy was a sign that she was his one true love and not a sign that she wanted him to get better. Rebecca decided that Josh proposing was the universe telling her that she didn't have to work on herself but should go get married. I'm a big believer in signs in fiction and in life. But it's really easy to interpret the signs in the easy way, in the way that requires the least amount of introspection and work. Being unselfish, much like relationships in general, is, more than a moment.