I think you handled it fine. It amazes how the WW will try to take advantage and play on the compassion of their LBH. Oh, I can nearly hear some LBS's spouses response to my statement, but I'm telling you that she was trying to manipulate certain feelings in you. I'm not saying she is in no pain! I'm sure she is. Her STD has been exposed, and she knows good & well that her H should be absolutely furious. So, she says she is too weak to decide if she wants you to go with her or not. Please! She wasn't too weak to text you. She wasn't too weak to tell you she was afraid, yada, yada.
Here's the thing. She is experiencing some consequences for engaging in sex with someone other than her H. I've heard that IUD's can be painful if not in properly in place. (Any thing that goes up in the va-jayjay that gets out of place is painful). IDK if it can cause that degree of back pain, but that's the doctor's call. Anyway, she's been exposed about the STD and the IUD. And just like other things the WW does that makes no logical sense.....she's going to temp check you. Mark it down.
It is not about what you feel should work in your M. It is about doing the work that gets the right results. Do what works!