After her friend accidentally discovers time travel through memory research, a habitually cautious woman risks her sanity and ultimately her father’s life by returning to her early teen years to prevent her Charlston-socialite mother’s murder.

Or:

After discovering time travel through memory research, a normally cautious (occupation) risks her sanity and the life of her father* by venturing into the past to relive her adolescence in order to prevent the murder of her mother.

*I would be tempted to tweak it to say her own life. Her father could be collateral damage, of course. Even if it jeopardizes her father's life, it raises the stakes (always a good thing!) if her own life is on the line, too.

Anyway, the logline shows her having a clear objective goal.

Or:

After discovering time travel through memory research, a normally cautious (occupation) risks her sanity and the life of her father* by venturing into the past to relive her adolescence in order to prevent the murder of her mother.

*I would be tempted to tweak it to say her own life. Her father could be collateral damage, of course. Even if it jeopardizes her father's life, it raises the stakes (always a good thing!) if her own life is on the line, too.

Anyway, the logline shows her having a clear objective goal.

"After the discovery of time travel through memory research,
a cautious (occupation)** re-lives adolescence
to prevent the murder of her mother at the toll of her (own sanity OR father's fate)**."