New playmate, with strings attached

I have a new playdate friend named Chloe. She is a neighbor, is just 2 weeks younger than me, and has got all sorts of great cool toys at her house. The only catch is that Mommy leaves after she takes me there, and a babysitter named Sara plays with both Chloe and I. I feel deceived because I am so elated when Mommy picks me up after school when I haven't seen her all day, and then she turns around and leaves me again! No one can take the place of Mommy, so I cry that I want to go shopping, to the meeting, or whatever it is that Mommy does when she leaves me. Being with her doing the most mundane tasks is still in my mind more enjoyable than doing anything "fun" without her! I've been crying "I want my Mommy!" a lot because I don't like this new situation. The only thing that has helped Sara calm me down is reasoning. She tells me that me wailing is not going to make Mommy come any faster, and may possibly delay her return. That made sense to me. See, I'm intelligent!