Help needed on jr pup please

Hi I have a 18 week old jack Russell bitch. We have her indoor and she is let out very often but she still goes poo and wee inside but especially in her bed.
I know it is not normal for a dog to soil their own bed, I was wondering does anyone know why she would do this???
She gets on great with our other dog who is 10 months old.

Also she is terrified of everything outside the house....cars, people and other dogs. She will cry/scream if another person(apart from myself, my partner or son) go to touch her.
She is a lovely dog while with me.

Has anyone got any help

Gratefully

Rosie