Friend tried on my contact lens for 30 seconds, can I still use it?

Even though your friend had "nothing wrong" with her eye there are still risks to your putting this lens directly in your eye after she has placed it in hers. Everyone has normal bacterial flora on the outside of the body. This includes the eye. The bacteria your friend has in her eye are different many times in type and genetics than those in your eye. Her body may have "learned" how to keep her bacteria under control. But when these bacteria come in contact with you and your immune system they may not be held in check. This can cause you to get an eye infection from foreign bacteria that do not cause infection in your friends eyes. Don't worry, though. All you have to do is put your contact lens through a complete disinfection cycle using whatever disinfection chemicals you use. This will kill any bacteria on the lens and they should be fine to wear.