On Friday (August 24), the R&B singer won the case against Foster, which awarded him primary custody of the two sons they have together.
Foster is interviewing lawyers for an appeal as she "feels the ruling was unfair", reports TMZ.
Foster apparently discovered that Usher's lawyer's law firm raised $1,278 (£808) at an election fundraiser in March 2008 for Judge Lane, who presided over the ex-couple's custody battle.
Foster is said to feel that the connection "may have influenced the ruling".
Lane's ruling means that their two kids will be spending most of their time with Usher, while Foster only gets custodial rights.
In July, Foster lost her son Kile Glover after a jet ski accident.
Watch the music video for Usher's 'Climax' below: