Melissa King -- the chick formerly known as Miss Delaware Teen USA until she resigned in the wake of a porn scandal -- is officially on probation ... after copping a plea in her underage alcohol  case.

The 19-year-old disgraced beauty queen plead guilty in a Maryland court to one count of possession of alcohol while under the age of 21 ... stemming from an incident last summer when cops found a bottle of Captain Morgan in her truck.

As part of the deal, King was sentenced to 1 year of unsupervised probation -- meaning if she stays out of trouble for the next 365 days, she stays out of jail.

Fun Fact -- King's lawyer told the court Melissa plans to go to college.

We have a feeling she'll be very popular in college.

Ex-Miss Delaware Teen USA Melissa King compromised her crown for a grand total of $1,500 ... cash she earned to star in her now-famous porn video ... TMZ has learned.

Melissa denied she's the one in the XXX video.  The guys behind GirlsDoPorn.com torpedoed her denial by posting a video of the 18-year-old beauty queen, reading a release form on their website ... in the clip, Melissa identifies herself by name.

What's more ... one of the guys behind GDP tells TMZ, Melissa was the one who reached out to the website to do the scene.

The GDP rep says Melissa was totally down to shoot additional scenes ... but they say her first try was frigid at best, so GDP passed.

The GDP rep says traffic was so insane the day news broke about Melissa's porno, they had to boost their server power.

Bottom line, there's hope for a sequel ... but now they might not be able to afford her.

She might have lost her crown ... but former Miss Delaware Teen USA Melissa King has just been offered a pretty sweet back-up plan ... $250,000 to promote a hardcore porn site.

As we reported, 18-year-old King resigned yesterday after a porno surfaced that allegedly featured King doing the dirty ... just months before she won the title last November.

Now, porn giant YouPorn.com wants to compensate her for the unfortunate situation -- offering to crown King the first ever "Miss YouPorn" and pay her $250,000 to tour the world promoting the website.

Funny enough, YouPorn's offer -- which was submitted to King yesterday -- doesn't mention having sex on camera in exchange for the fee. Not a bad deal.

It's unclear if King plans to accept her new crown.

Miss Delaware Teen USA Melissa King has officially given up her crown today ... after a porn surfaced on the Internet that allegedly features the 18-year-old beauty queen.

A rep for the Miss Teen USA pageant just released a statement, claiming, "I would like to confirm the Miss Delaware Teen USA pageant has received a resignation letter from Miss King’s attorney."

King reportedly denies it's her in the hardcore sex footage -- but the girl in the video looks and sounds EXACTLY like King.

In the vid -- shot some time in June 2012 -- the girl addresses the camera, claiming she turned 18 a couple months beforehand in March, which is King's birth month. The girl also describes her favorite sex position ... before the actual sex begins.

King was crowned Miss Delaware Teen USA in November ... four months after the sex footage was shot.

A rep for the pageant tells us, they have already reached out to the first runner-up Hailey Lawler in order to replace King.

Walks like a duck, talks like a duck ... resigns like a duck.