NMum blocked me on Facebook

As the title suggests, I found out today that my mother has blocked me on Facebook. I am not especially bothered by this, but seeing as she likes to pretend like there is absolutely nothing wrong in our relationship (despite me directly confronting her nearly 18mnths ago and having had minimal contact since), I would like to find out why. Here is my question, when I msg her should I say “why did you block me?” - therefore asking for a reason, or “did you block me?” - giving her the chance to lie and deny before I present her with the facts. I’m pretty good at dealing with my mother these days, but would just like some group guidance. TIA!!!