"Miley is not taking any sides on this. She has been upset recently," a source close to the singer tells PEOPLE.
"She's trying to keep everything private while her family works through this," the source says.
In divorce papers filed by Billy Ray Cyrus on Oct. 26, the country singer seeks to share custody of the three minor children he has with wife Tish: Miley, who turns 18 on Nov. 23; Braison, 16; and Noah, 10. (The pair also have two older children Trace, 21, and Brandi, 23).
Tish, 43, headed to Nashville from her L.A. home earlier this week, while Billy Ray, 49, was in Indianapolis on Monday night to sing the national anthem for the NFL's Monday Night Football Colts vs. Texans game.
Next up for Miley: a trip to Madrid this week in anticipation of her performance at MTV's European Music Awards on Sunday.
Reporting by MICHELLE TAN