Oral steroids will stop a severe reaction but nursing complicates that I think. My husband is like you and has ER visits anytime he gets exposed. It takes him over. Bendryl (oral) can help with itching so you can sleep and etc. though it won't fix the rash.
I *think* with poison Ivy you have to be exposed once before you react. I don't think she's likely to get it. Keep any blisters covered/not contacting her if you can.
I've heard good stuff about these: http://www.ivydry.com/
I had also found some type of cleanser not long ago that you could use to prevent. My husband thought it looked promising but I can't remember the name or find the link again.
For prevention my husband is just extremely careful. He hasn't had it in many years for that reason. Can you ID ivy? is it around your home? If hiking or similar stay on cleared trails/free of Ivy and wear long pants if you can. Wash any clothing that might have come in contact. That stuff I found could be used for washing things too or wiping down things like shoes. I wish I could find it again.