Saly Greige took to her Facebook page to declare that Israel's Doron Matalon had pushed her way into a now widely-circulated photo showing the Middle Eastern beauties with Miss Japan and Miss Slovenia.
"Since the first day of my arrival to participate to Miss Universe, I was very cautious to avoid being in any photo or communication with Miss Israel (that tried several times to have a photo with me)," Greige wrote in English on her page.
"I was having a photo with Miss Japan, Miss Slovenia and myself, suddenly Miss Israel jumped in, took a selfie, and put it on her social media."
The offending photo, taken in Miami where the Miss Universe pageant is staged, appeared on Matalon's Instagram account on January 11.
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It shows Miss Israel with a beaming Miss Slovenia and Miss Japan, and Miss Lebanon, who appears to be gritting her teeth.
Matalon responded to the controversy herself on Sunday, saying it made her "sad".
"It doesn't surprise me, but it still makes me sad. Too bad you can not put the hostility out of the game," she wrote in English and Hebrew.
Lebanese media picked up the story, running Greige's allegations that Matalon had "photobombed" the selfie, and local social media users both defended and attacked their beauty queen for the picture.
Israel occupied parts of Lebanon for 22 years until 2000, but the two countries are still technically at war and their armies occasionally skirmish along the UN-designated withdrawal line.
Israel fought a bloody war against Lebanon's Hezbollah in 2006, which killed more than 1,200 people in Lebanon, mostly civilians, and some 160 Israelis, mostly soldiers.