This at the time under 18 year old pre-Twilight days actress had an affair with this B- list mostly movie actor and it broke up his marriage to this A list mostly movie actress wife. Not Kristen Stewart.
Twilight actress: Nikki Reed
B- list actor: Ryan Phillippe
A list actress: Reese Witherspoon
Source: http://www.crazydaysandnights.net
Read more on these Tags: Nikki Reed, Reese Witherspoon, Ryan Phillippe