Lauren Conrad's Halloween look? Practically perfect in every way.

The author/fashion designer, 26, hit Matthew Morrison's Halloween party in Hollywood Sunday, Oct. 28, dressed as Mary Poppins. Her boyfriend William Tell coordinated his costume, dressing as Bert from the classic musical.

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"[William] is super sweet," a source tells Us Weekly. "He seemed to really tend to her the entire party. Lauren seems extremely happy with him."

With her law student beau by her side, Conrad hardly noticed the arrival of her ex-boyfriend, Kyle Howard.

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"They are so far past it, it wasn't that awkward to see him," an onlooker reveals. "It really wasn't a big deal."

Conrad and Howard called it quits in June 2011 after three years of dating. Six months later, she met Tell after pals set them up together on a double date.

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"They really connected," a friend told Us at the time, revealing that Tell "gravitates toward dynamic women."

"He doesn't date just to date," his ex-girlfriend Sadie Murray also shared. "He's either deeply in love or he's on to the next thing . . . He's the kind of guy you marry."

This article originally appeared on Lauren Conrad Dresses as Mary Poppins, Avoids Ex Kyle Howard at Matthew Morrison's Halloween Bash