Went out with a girl, first date went great, had drinks / fun.

Second date invited her over, made dinner, had sex.

Third date met up at her place and then went to a winery during the day. On the way back asked to hang out (aka go inside her place) and she said she was busy and had dinner with her friends that night. Not sure someone into me would plan to go out with friends the same night we are having a date during the day, especially if she wanted sex? I feel like a chump by having sex on the 2nd date but not the 3rd. Not sure if it was just an excuse or what. Am I thinking too much? Thinking of just not texting to see what she does.