Wow, this is a strange situation in so many respects. For starters, I do think the provider has not done her own homework. I've not heard of this kind of wart. But the first thing I would do is google everything I can find if one of my daycare children had this. I always check things out when parents tell me about a problem. It's not that I want to doubt parents. It's just that in the world of daycare, we do see a lot of parents that refuse to spend the money on taking care of things. It's also scary to have our own children and the rest of the children be repeatedly exposed to something that might be catching. I am aware that warts are caused by viruses, so I would be concerned. But as I said, I haven't heard of these.
That said, I find it VERY difficult to believe that your communication broke down to crying over this one issue. You haven't said if it was your crying or hers. But in no way should anything become this emotional when trying to deal with a daycare parent and vice versa for you. Either one or both of you are having a huge problem with communication. Without being there, I will reserve judgment.
As far as counting the bumps go...I'm sure she has. She's questioned your decision to care for them the way you choose. She probably feels justified and thinks it's a big deal. But I almost can't blame her for lying about it if the crying and tears came mostly from you. Without knowing how defensive you may have gotten or how defensive she got, it's hard to know if she's just a liar at heart or if she's just trying to avoid another scene.
I had a daycare child that got these huge wart things on her toes. I was so concerned when they were so large and I was afraid they would interfere with her shoes since they were so big. I trusted the parents so much I didn't do the googling. We had a good relationship and I really wasn't concerned because they were extremely strange and in 24 years I've never seen them. So I didn't think the whole daycare was about to get them. I wonder if they are the same. If I saw them spreading to the rest of her body, I'd be very concerned too and maybe question a choice to leave them.
I'm sorry that this situation has gotten so blown out of proportion. But I support your decision to try and keep things calm and cool until you move. Why make them get used to a new daycare and then have to do it again later? If possible, just try and tell her that you are very pleased with her care of your kids and the girls love her house and you trust her. But that you need to be her parent and for her to respect your bounderies. Does she know you'll move at the end of the summer? Despite her behavior, she does deserve to know that.