She obviously did eat something or absorbed enough desel fuel to cause some poisioning to her system.
Unless the bird had eaten somthing toxic that should not have made her sick. Our Boston Terriers, being carnivores would actually be healthier if they ate raw birds (usually quail or chicken would be ideal) but if the bird had eaten say some rat poison or simialr and it killed the bird then most likely that was not the puppies problem. More likely the fuel was!
IF there are chemicals ANYWHERE on your property that any dog could get into then no dogs should be allowed to come into contact with them.
Can't you take the Boston for a walk with you and the sheltie on the property? She NEEDS to be outside breathing fresh air, getting sunshine and LOTS of exercise but yes, it needs to be supervised.
