Okay but what the ****, why would you hold her BY THE TAIL. UPSIDE DOWN. you're lucky she didn't drop her tail. You could've just put her in a clean container and looked at her from below. Like, I just don't understand why you thought that was a good idea...
To the above... Many people do this, myself included. It's the best way to get a look at the underside. I've never had one come close to dropping a tail. The geckos front feet are still on a solid surface, so I don't see a problem.