To be through the roof

As earlier commenters have noted, the original "through the roof" idiom seems to have been "go through the roof," which Christine Ammer, The American Heritage Dictionary of Idioms, second edition (2012) defines as follows:

go through the roof 1. Also, hit the ceiling or roof. Lose one's temper, become very angry, as in Marge went through the roof when she heard she'd been fired. {Colloquial; first half of 1900s} 2. Reach new or unexpected heights, as in After the war, food prices went through the roof. {Colloquial; first half of 1900s}

Evidently, the intended meaning of "through the roof" in the example that the poster asks about is something like elated, excited, highly enthusiastic, or very positive. This is not an especially big jump from Ammer's meaning #2 of "go through the roof" ("reach new or unexpected heights") although one might expect to encounter transitional instances in which forms of "to be" replace forms of "to go" in expressions that mean something like "to be extremely high." A Elephind search of U.S. and Australian newspaper databases turns up instances of this type from as early as 1994.

From "Back to Business, Say Top Broncos," in the Canberra [ACT] Times (March 25, 1994):

"The forwards haven't been shirking it," Johns said.

"Their work rate has been through the roof because of the ball we've turned over. "We are certainly creating a lot of work for the forwards."

From Robert Trevino, "Businesses Basked in Clinton Spotlight," in the Coronado [California] Eagle and Journal (April 7, 1994):

Thy [employees of a T-shirt company] made several shirts for the employees, then ended up having more printed due to customer demand. And though the store’s manager said business didn’t necessarily increase a great deal, the enthusiasm level was through the roof.

“It was so much fun, and it interested a lot of people,” said Jill Howser, Bullshirt’s manager.

From Martha Martin, "There's No Place Like Home," in the [Pueblo, Colorado] USC Today (November 6, 1996):

Now I know this all sounds a bit strange and unusual, but I actually enjoyed the convention more than the city. I found the people of LA rude and inconsiderate.

And the fear factor was through the roof. I mean to say I felt very insecure and confined. The city of Los Angles is very spread out. You can look in any direction and see only city.

From Jay Adya, "Shots in the Dark: Can't Tennis Become More Like Golf?' in the Columbia [New York City] Daily Spectator (September 10, 1997):

Only two days ago, in the biggest single sporting event in New York, Australian Patrick Rafter capture the U.S. Open with a dazzling display of attacking, aggressive tennis. But did anyone care? Ratings, regardless of the lack of American participants, for the finals of a major championship, akin to the PGA Championship or British Open in golf, should have been through the roof.

From "Men's Squad Strong Once Again," in the Stanford [California] Daily (January 27, 1999):

"For the distance guys, indoor is a good time to make sure everyone is race ready when the outdoor season comes along," said Riley.

"But indoors, everything is on a smaller scale and everything seems to happen just a little quicker. The venues might be small, but the intensity is through the roof."

And from Trevor Henderson, "Build a Strong America: Good Citizenship Counts,"in the Rappahannock [Virginia] Record (June 6, 2002):

Once there was a boy named Bobby Joe. Bobby Joe was one of the smartest boys at LMS. He treated everyone with respect. He treated everyone with the same amount of respect, even his family. His responsibility level was through the roof, but his dependability level was to the moon.

Elephind searches yield dozens of matches from the past two decades for "[to be] through the roof"—but the thing thus described is in every case (as in the examples above) some emotion (such as fear, anxiety, excitement, confidence, or tension), some level of exertion (such as energy, intensity, work ethic, or effort), some objectively measurable quantity (such as prices, a budget, spending, train ridership, television ratings, or blood pressure), or a qualitatively variable but not mathematically measurable entity (such as sex, partying, a difficulty, or an ego). In no case that I could find, however, did an article refer to a person as being "through the roof."

From this I conclude that saying that a person is "through the roof" remains an unusual idiomatic expression in current US and Australian English. It wouldn't be shocking if expressions of the form "Your mother was through the roof" (meaning "Your mother was very excited") caught on as a specific form of the more general usage of "[to be] through the roof" in the sense of "[to be] quite high or very great." But so far, this particular usage does not appear to be widespread; indeed, it may be extremely localized or even, perhaps, just an idiosyncratic phrasing used by a smattering of unconnected individuals.