It also depends on how long and how frequently you've smoked. If it was one hit, one time only and ever, should be out of your system for a urine test within a couple weeks, if not days. If you're asking how long you stay high off one hit...depends on the weed and how often you smoke. But, usually not very long.
Manufacturers often design e-cigarettes to look like regular cigarettes, but they contain no tobacco and don't require a match -- or any flame at all. An e-cigarette is a battery-powered device that converts liquid nicotine into a mist, or vapor, that the user inhales. There's no fire, no ash and no smoky smell. E-cigarettes do not contain all of the harmful chemicals associated with smoking tobacco cigarettes, such as carbon monoxide and tar.
You also can tell your daughter that one study found five minutes of vaping lowers lung function as much as smoking a conventional cigarette. In its favor, this cloud of vapor doesn't contain the 60 known carcinogens found in tobacco smoke, and it may be a way to kick tobacco (it works for some folks). But as a general rule, putting anything besides relatively clean air into your lungs can lead to a roster of complications.