Today, Kristin Cavallari wished a happy birthday on Twitter to her former Hills cast mate and published author Heidi Montag.

Heidi said thank you! And love you!

Does Kristin love Heidi back? While she never showed outright contempt for her on The Hills, Kristin did not invite Heidi to her 2013 wedding to Jay Cutler.

Kristin explained to America’s Star magazine at the time:

[The wedding is] going to be family and really close friends. If the wedding were bigger, I would have loved to invite Audrina, Stephanie and Heidi.

Damn. Last on Kristin’s list of women one step removed from “Lauren Conrad.”

Happy birthday.

This has been 500 Days of Kristin.

[Photo via Getty]