Kathy Selden (Debbie Reynolds)’s Timeline and Summary

Kathy meets Don when he jumps into her car in traffic, and she gives him a ride home.
On the drive, she lies about being a stage actress and insults Don by talking smack about lowly movie actors.
While performing with her fellow Coconut Grove dancers at R.F.'s party, she totally gets busted by Don. Then she accidentally creams Lina in the face with a cake. She runs away in embarrassment.
A few weeks later, after getting hired as a backup dancer for another Monumental Pictures movie, Kathy runs into Don on set. They apologize to each other and start falling in love pretty much immediately.
Kathy agrees to dub Lina's speaking and singing voice in order to save Don's next movie.
At the movie's premiere, Don and R.F. order Kathy to sing for Lina again. She does so, but under protest, telling Don she never wants to see him again.
Don, R.F., and Cosmo reveal that Kathy's the one singing, thereby exposing Lina as a big ol' fraud.
Kathy tries to runs away in embarrassment again, but Don stops her and wins her back by telling the audience that Kathy's the real star of the movie, thus saving her career.
Kathy and Don admire the billboard for Singin' in the Rain, a new movie in which they co-star. Aww.