Think back of what you touched of hers including being in her home,car, towels, etc and you might be able to identify where the oil might have been picked up from. I suspect the dog personally!

Remember the rash is a delayed response from your immune system attacking this oil that has bonded with your skin proteins. The rash forms much later (12-36hours) after the oil has already bonded to your skin. Unfortunately, the oil can bond to the skin rather quickly and then becomes very difficult to remove. Literature cites anywhere from 3 mins to 1 hour. For most of us, its about 15 mins before the oil has bonded. Before it bonds, soap and water, rubbing alcohol, etc will remove it.

By the way, this delayed response is one of the tell tale signs of a poison ivy rash not to mention the uncontrollable itch. The big problem is how do we know it was a delayed response when we can not see or know when the oil touched us! Many of these contact dermatitis rashes looks very similiar unfortunately.