Heidi Montag has denied a report that she failed to show at her sister's 26th birthday bash over the weekend was because she wasn't getting paid for the appearance.

[It's] absolutely not true," The Hills star's representative told Access Hollywood about a Tuesday Fox News report that Montag had refused to attend the party unless she was paid an appearance fee.

According to the representative, Montag celebrated her sister's birthday with her at a separate event.

Montag's sister -- former I'm a Celebrity... Get Me Out of Here! participant Holly Montag -- celebrated her birthday on Saturday night at Los Angeles' Empire Hollywood.

However Heidi and her husband Spencer Pratt did not appear, leading to the report that it was because they wanted to be paid for the appearance.

"Holly was really wishing that her sister could just be a sister and stop by her birthday party, but Heidi only goes places if she is getting paid," the source told Fox News. "I mean, this is her sister and she wouldn't even show up without a fee. That's disgusting."

While Heidi might not have been at the party, her sister-in-law and The Hills co-star Stephanie Pratt was -- and landed in some trouble with the law after the event.

She was arrested around 3:45AM on Sunday in Hollywood on suspicion of drunk driving.  The 23-year-old was charged with a misdemeanor and transferred to the Van Nuys jail for booking and was subsequently released around 10:30AM Sunday morning.