Britney Spears' terrible week has got just a little worse today, hours before a judge is to review his decision about the custody of her two kids. In Touch learned exclusively that Britney's biggest defender, her assistant Alli Sims, packed her bags and abruptly moved out of Brit's Malibu home this morning — and possibly out of her life.

Alli, 26, has been Britney's biggest supporter throughout her rehab stay and her bitter battle with ex-husband Kevin Federline over their sons, Sean Preston and Jayden. Insiders tell In Touch that she has finally had enough. "Alli wants her own life and own career," says one. "She can't take anymore of the drama."