Yes, chicken pox is highly contagious and can be serious as an adult, so do avoid her. The good news is that if you have ever been exposed to it before, you probably had it. People think you have to have the full blown disease, but sometimes it is just a minor thing that goes unnoticed, with only one pox sore that seems like a pimple.
I have no memory of chicken pox, but did not get it when my kids had it. One son had pox all over and he was miserable. The other had maybe 5 sores, none of them on exposed skin.
The shingles vaccine is also live virus, so you cannot get that either while on Humira.
Jan