The Lake County jury took just four hours to convict her of killing Rhoni Reuter and her unborn child in 2007.
"This was an execution, a cold-blooded murder. This verdict brings justice," said Mike Waller, Lake County State's Attorney.
Jealous of Gayle relationship with Reuter, Yang, learned how a silencer for her .09 Beretta after buying a book on amazon.
Then after renting a car with her ex-boyfriend's credit card, she donned a disguise and went round to Reuter's Deerfield condo and blasted her six times, making sure she killed the baby, who Reuter had named Skylar.
Gayle, who had admitted having a sexual affair with Yang, said outside the courtroom he had his own regrets about the death of Reuter and his baby.
"At least I feel Rhoni and the baby are at peace," said the 10-year Bear veteran.
The Chicago Tribune reports that the tape recording of Yang discussing the killing with her long time friend Christie Paschen proved to be powerful evidence for the prosecution.
including disposal of the murder weapon.
"They are never going to get it," Yang said, talking about the murder weapon. It's under tons and tons and tons of Chicago trash."
Yang, who showed no emotion as the verdict was read will be sentenced next month.
It is not known if she will appeal.