Have Mary-Kate and Ashley Olsen finally had enough of being joined at the hip for the past 21 years?

Relations are said to be strained between the tiny twins after a number of disagreements over business and real estate decisions – that, and Mary-Kate’s “mood swings.”

“They’ve finally had enough of each other,” a friend tells the National Enquirer. “They just don’t see eye-to-eye anymore and are tired of constantly butting heads.”

“Ashley isn’t an angel, but she’s tired of having to take care of Mary-Kate. One second Mary-Kate is maniacally happy, and the next she’s sobbing. Her mood swings are dragging Mary-Kate down, and finally, Ashley’s decided she doesn’t want to go down with her.”

The main bone of contention is said to be their estimated $100 million personal fortune.

“Ashley’s been considering separating their assets and trusts and getting her own business manger,” adds the insider.