Yahoo! chief Marissa Mayer is far better at being a tech and biz whiz than a house host, according to sources.

Mayer has been a mentor for three years running to visiting female execs from developing countries as part of Fortune and the US State Department’s Global Women’s Mentoring Partnership. But people familiar with the respected program tell us one mentee’s stay with the Google VP turned into an episode of “Home Alone.”

According to multiple sources, Mayer, 37, unlike the other mentors in the program, asks that mentees stay at her home rather than in hotels. “Marissa wants them to have a more immersive experience,” a source explained.

But when a recent Middle Eastern mentee arrived in the States for the very first time, she found herself killing time in the mogul’s Palo Alto pad for days with no company or guidance.

“Marissa’s mentee arrived in California, and two days later was told Marissa and her husband were leaving town,” said a source. “They left for four days, and this woman was just left there, having never been to America, with no real support.”

The source added even after Mayer’s return, the mentee’s interaction was “mostly with personal assistants,” and one astonishingly instructed her “not to eat Marissa’s food.” After a week and a half, the mentee asked to move to a hotel to finish the two-week trip.

Another source contends there was “an issue ” and “it didn’t work out,” but that Mayer — who has a $59 million compensation package at Yahoo — “has always been incredibly generous and involved with mentees” who’ve “had the time of their lives.”

The venerable program, an extension of the Fortune Most Powerful Women Summit, has mentored more than 200 women from 49 countries.

A Fortune rep told us: “[Marissa] is one of our most generous mentors. . . . she has gone to extraordinary lengths to support her mentees both during the program and beyond.”

A rep for Yahoo did not respond.