Lindsay Lohan was reportedly "not happy" that on/off girlfriend Samantha Ronson recently went out with Nicole Richie.Nicole, 28, and boyfriend Joel Madden, 30, recently went out dancing at Playhouse Hollywood with Samantha, 32, where they reportedly did shots of lemon drops and danced in the VIP room.A fellow clubgoer said that Sam and Nicole were acting like best friends and Lindsay was not happy about it.An insider said to FOX411: "When Lindsay found out that Sam was out with Nicole, she was not happy!"Since Lindsay's return to court last week, she has to be extra careful for probation, and [hearing about] Sam out with Nicole hurt her."The pal added that there is a rift between Nicole and Lindsay and Sam is stuck in the middle of that dispute.The pal said: "Nicole has made it very clear to Lindsay and to their mutual friends that she wants a better life for her. Nicole hopes Lindsay will get it together and change her behavior, but until she makes a change, Nicole avoids her."Sam and the rest of the Ronson family have remained close to Nicole, Joel and his brothers."The source added: "Sam loves Nicole and Joel and she cares deeply about Lindsay. She in no way wants to hurt her, but Sam will not drop her friendship with Nicole."Lindsay takes her hanging out with Nicole personally [and] as an attack on their on/off relationship."source: Splash News