Kirsten Dunst’s hard-partying ways drove her and former beau Jake Gyllenhaal apart, a pal dished to Us Weekly. Dunst, who entered Utah’s Cirque Lodge rehab earlier this month, and Gyllenhaal dated for three years before calling it quits in 2005. “Jake was turned off by all the partying,” the pal says. Multiple sources confirmed the “How to Lose Friends & Alienate People” star regretted the breakup and started going out and drinking even more after the split. “There was no such thing as ‘just the one (drink)’ for her,” a source said. Dunst’s rep denies that drinking led to the 2005 breakup.