rachel is not necessarily sad, but she mentions that her foot is sore, which suggests she might be in discomfort or pain.
rachel's team plays volleyball.
mary wants to come and watch the volleyball match.
rachel can't play because her foot is sore and she moves slowly.
rachel and mary both mention that they dislike using knee pads, but it's not explicitly stated why. it seems like a personal preference.
yes, mary likes playing volleyball. she expresses her love for the sport and is enthusiastic about the opportunity to play with the team in the evening.