She was relieved to hear applause, not awkwardness. She didn't dare look in any direction but straight ahead, even though she knew her family would be near the front. This was her professional debut; she didn't want any reason not to be hired again.
It was over very quickly - walk, backstage, bow, end of show. Once the show had ended, she felt able to look around, and in the third row, she found the faces she'd been looking for. At least there was Valjean. Cosette might have been too short.