It's okay, take it easy cute spider girl.

This seems to be Vaginismus

"Vaginismus is an involuntary tensing of the vagina. People experience it at the start of sex, while inserting a tampon or while getting a pelvic exam. Vaginismus can make intercourse painful (dyspareunia)."
Wikipedia

Maybe it was because of the last few moments when he spoke and got all serious, making her nervous. But we can't blame him for that. It’s her first time, which makes sense she’s struggle a bit.