She wouldn’t cut the mustard as a hardened criminal.

A thief who swiped a bottle of ketchup from a New Jersey restaurant was so wracked with guilt — and suffering from bad karma — that she secretly returned to drop off two containers of Heinz.

“I hope returning two new bottles will restore some [luck] for me, and I can stop carrying around this guilt,” wrote the contrite condiment klepto in a note left with the ketchup outside a door at Perkins Restaurant & Bakery on Route 9 in Forked River.

The thief — who workers at the eatery insist is a young woman, judging from her penmanship — admitted in the note that she had no good reason to steal from the Lacey Township restaurant.

“A few weeks ago, I had taken one of your ketchup bottles off the table because for some odd reason I thought it’d be ‘risky,’” said the note, which was posted to a community page called Lacey Township Chatter last week.

“I am as square as they come and this is the worst thing I’ve done,” the letter-writer said.

“Well, a few hours I did it someone crashed into my car, and since then, my karma, luck, and life have been s–t,” she acknowledged.

The writer said she hoped that her repentant offering would turn her luck around, and, “Again, I’m really sorry if I inconvenienced you the same way my life has been inconveniencing me.”

The culprit didn’t leave a name but signed off with, “From, an awful person.”

Restaurant manager Charlene Reebe told The Post on Monday that she found the pilfering diner’s penance Wednesday night while checking the site’s doors at closing time and cleaning up trash left around outside cans.

“There was just a normal, little gray Walmart bag on the side of a can, on the ground, and I remember thinking to myself, ‘Why didn’t someone just put it in the can?’ ” Reebe said.

“And I open it up, and there’s a letter, receipt and two bottles of ketchup in there.

“I was very surprised,’’ Reebe said.

She said no one in the restaurant had noticed the bottles were even taken.

The receipt showed the thief paid $2.78 apiece for the 32-oz. ketchup bottles — which are 12 ounces more each than the 20-oz. Heinz that the eatery puts on its tables.

“The minute you put on the news these days, it’s always terrible things happening. and this just was something nice,’’ Reebe said.

She said she remembered thinking “that she’s probably a very nice young lady and that she does have a conscience.

“What I’d say to her is she’s a good example of how kids should think things through before they do them, and even if they do make a mistake, that they own up to it,’’ added the 54-year-mom of a son and daughter, both in their 20s.

The restaurant’s owner, Maria DiLeo, said she posted a photo of the thief’s letter on Facebook along with the tale in the hopes that the perpetrator sees it and knows all is forgiven.

“Hope all goes better for you. Lesson learned,’’ DiLeo wrote.

She told The Post on Monday, “How could you not forgive someone like that?

“I was like, this poor kid, she must feel terrible,’’ the owner said, speculating that the thief is local, given she got the ketchup at the nearby Walmart.

The restaurateur said she even has something to offer the thief — a job.

“I would hire her in a second,’’ DiLeo said. “Because if you do something like that, you’re not an awful person. You’re an honest person.’’

The thief’s note, receipt — and two bottles of ketchup — are now on display in the South Jersey eatery.