How can I get over giving my dog up?

I had a year old cocker spaniel that I just returned to the place I got her. She had some kind of mite and her coat was patchy with many bald spots some with blood ozzing out. I tried to treat her but she just would get worse. Im taking care of a baby at jhome and I.was afraid the baby might get sick from my constant handling her. I did wash my hands each time. So I told the man who sold her to me to just take her back. He couldnt believe it. My other toy poodle misses her now hes all alone hollering for her. Do you think I made the right decision. I couldnt afford all the treatments for her mites.