She was immune to Captain Trips, and escaped New York City with Larry Underwood through the Lincoln Tunnel. Rita had lived a pampered life and quickly showed that she was not ready for the post-apocalyptic world, which results in tension between her and Larry.
She is discovered rather early in the early Post-Plague time in the park with others of Manhattan, striking up a cautious relationship with Larry that quickly evolves into a sexual one. Being older than him and suffering from addiction to various medications, Rita's mental state isn't as stable as it appeared at first, prone to bouts of depression and abandonment issues, she begins to cling to Larry as a form of support. It's learned here that her husband was distant and - from her reaction when spilling coffee on Larry and after being unable to keep food down - that he was likely abusive to her as well.
During their first attempt at leaving New York, Rita wore footwear that wasn't meant to be used for long stretches over differing terrain and injured her feet enough to have them begin bleeding, this issue quickly escalated to a loud and aggressive argument between her and Larry, where she told him to leave. On his turning away from her she left the area, though did later meet back up with Larry in an attempt to leave the city again.
Several days after escaping New York City, Rita commits suicide by an overdose. This occurs while Larry is sleeping next to her and the discovery of her corpse leads to a Larry having a breakdown.