I need some help to understand the plot of this movie

SPOILERS (possibly)

My understanding of the plot is as follows:

Eileen Wade is having an affair with Terry Lennox. Terry's wife Sylvia finds out and Terry kills her (start of film).

Terry takes Marty Augustine's money to Mexico. Terry fakes his suicide and hides out there.

Eileen returns the money to Augustine saving Marlowe's life. She goes to Mexico to live with Terry not knowing that Marlowe killed him (end of film).

Questions:

1. Marlowe doesn't know Eileen. Eileen doesn't love Roger any more. Why does Eileen go to Marlowe to find Roger?

2. The money is in Mexico. Eileen isn't in love with Marlowe. Why does she save him and how does she get the money?

3. What happened to Marlowe's cat? Actually, I know the answer - the cat has gone to the girls' apartment to enjoy some catnip brownies! :)