I see you are in Greece and I am not sure of the rules/regulations for Yorkies in your country but in the US it is standard for them to stay with their mom until 12 to 14 weeks old. With this in mind you will probably hear many member telling you that she is too young to be away from her mom. But that is not your issue................
I'm guessing that she is probably ovewhelmed by the new surroundings, does not know where her place is at your summer home and so she is hiding and shaking.
My suggestion would be to make sure she is warm and keep her close to you as much as possible. Are you crate training? When you are not able to keep 100% attention on her she should be put back into her crate so that she feels safe. A puppy whether at home or away should not have free rein of their environment for their safety as well as house training. Make sure she is eating and drinking but it would not be unusual for even an adult dog to have a change in eating, drinking and sleeping habit with travel. All of the new surrounding are just too much stimulation for her. If this is someplace that you go to often it will eventually become like home but for now it is like the first day she was brought home to live with you and your family.