Ashleigh was still partially asleep and she followed him into the deeper kiss without taking their location into consideration. It felt natural to react to him - to sigh when he was touching her, to want a little more when he was kissing her.
She wouldn't usually be this disrespectful. She would tell him that they couldn't do something like this under his parents' roof. Right now, though, she just really wasn't thinking... not about anything other than how good it felt to be close to him.