Billie was a mother of four, of course. She had originally started using the app because she had lost custody of her son Orion to her first husband, now her ex-husband. This wasn't what had really happened because Roger used the app. Billie didn't remember it, but she was originally Bill, and she was originally a father of four, not a mother, and her child was originally named Abby, but it was close enough.
She looked at the app. She had gained custody of Orion using the app, but she still didn't have custody of the other three. They were triplets which was rare, and they were 15 years old, so they would become adults in a few years and custody wasn't so important. With her new child, she would become a mother of five. (She did remember accidentally using the app to become pregnant, since she did that herself, but now she remembered doing that while being Roger's wife.)
But the app didn't say that with the extra child, she'd become a mother of five. It said she'd become a mother of two. What had happened to her other three children? Maybe she lost custody so they didn't count as hers? No, the app had called her a "mother of four" before and she didn't have custody then, so that wasn't the answer. Did they disappear at some point? She changed the sentence from "two" to "five" and glanced back at some movement that caught her in the corner of her eye. Three fifteen year olds were sitting in the back of the van. She recognized them and at least that part had been fixed.
She generated another sentence while Roger was driving them home. This time she happened to have the phone pointed at Roger, and the sentence said, "Roger wanted revenge, so has turned Bill into his pregnant wife."
What? Did Roger change something? Billie did argue with Roger a lot, and their marriage wasn't working out, so he could certainly be mad enough to want revenge. But she was named Billie, not Bill... Did the app change her memories? If Roger had used it, she might not really be his wife or a man at all. Yet it all was reality now. She didn't remember being a man. As far as she was concerned she was born a girl and she had a real wedding. Even if it was all the result of the app she couldn't just get rid of her life by undoing something she didn't even remember.
Maybe she could change some of it back just to see what it was like, though. If she changed 'wife' to 'girlfriend' it would just change the marriage. Or if she changed 'wife' to 'husband', it would be awkward to be a pregnant man but she'd be one step back towards a reality that she forgot. Another possibility was to make Roger into a woman--maybe that would make their relationship better. There are not a lot of women named Roger, but it was possible and she was attracted to women (which made sense if she was originally a man named Bill).