The 31-year-old actress stepped out following the split on Thursday afternoon (January 11) in West Hollywood, Calif.
According to Us Weekly, the break up took place over the past six months.
“They had been slowly breaking up for the last six months. It was very drawn out. They took forever to actually break up,” the source said.
They added, “It just took way too long to pull off the bandaid.”
Lena and Jack dated for five years after being set up on a blind date. Jack is reportedly seeing someone else.