Not necessarily. There's plenty of fine diamonds with thin girdles. "Very thin", or "extremely thin" is not as desirable as thin+, but if the distance of the area in question is not that great, you probably don't have a problem.
Especially if it's a smaller diamond, such as the 0.18 side diamond you're talking about. There's just not a real big chance that a small area like that is going to take a pinpoint hit strong enough to make it chip.
Be happy...don't worry.