My grandparents are going out of town but not taking me with them. I’m going to be alone! 😭😭😭

My grandparents are going out of town for a week and they said that they both in a vacation and some time together. They told me I’m gonna be in charge of the house for a whole week trust me enough. I mean that’s great but my mom side the family and I really don’t get along and they don’t really talk to me either. My grandparents are the only people from my mom said I talk to. I’m afraid that my cousins are going to come over and take advantage of me. I can’t believe I’m gonna be by myself and not taking me with them. My grandpa said, “Oh child please! You’re almost 20 years old. You don’t need a babysitter and your old enough to stay at the house by yourself. You’re capable so cut the crap. You’ll be fine.”
Then grandma said, “You don’t need us. You know not to let anybody in the house and lock up the house when you leave. You’re 20 not 10. Act like an adult. You were by yourself when your dad and girlfriend were out of town.”
They have a point but I’m autistic and something might happen to me. What do I do?? That was a while ago.