If you envision that Sara would look like a youthful, natural beauty, then here's a preset to make her pretty without mods. 

Her MEA version is up on https://masseffectarchives.com/#user/1002509187198/playthrough/1433184919/gender/female

You have two options on how to use: manually setting the sliders or setting up an account on MEA archives.
Both probably take the same amount of time ish if you had never made an MEA account. I like manually since I am old school.

Manually means you download the file and open the text and follow the values and pictures when you do character creation by either starting a new game or whenever you are aboard the tempest at the infirmary near where Dr. Lexi normally is.

The other way is create an MEA archive account and link it to your EA account and then using that MEA link and setting that you want that face for your next playthrough. I have actually never done that so unfortunately I don't know if it works mid game or only for new games where you have this option of 'import from archives' on the character creator screen. The MEA archives websites says it is only for a new game start but it could be outdated information.

Hope that helps!