I used to do home support to children when i worked with the childrens hospice, i know just from working with these families what a major thing it is for then to trust you before they can even think of leaving their child with you. I think you have to be honest with yourself, if you did leave Beth with this lass would you be able to relax and enjoy the little bit of 'time off' that you would have or would you be worried? If you arent going to be able to relax then is there any point? Im sure beth would pick up on your anxieties as well.
Not an easy decision so sending you a few (((hugs))) to