Jim, I had something similar happen to me recently. I was having, as you put it, a bad day, and had a really good and well meaning friend (one of very few people that "know") ask me the following day if today was going any better for me. My initial response was panic. Fortunately, he asked me in a text, so I had time to get over that initial reaction before saying anything.
My fear stems from being worried that I'm not covering as well as I think I am. That I look like the nutjob I sometimes feel like - out in public for the world to see. I try really hard to keep my PTSD symptoms to myself, to not allow them to interfere with friendships or work, and I've always felt like its something I need to hide. The fact that someone could see I was struggling, left me feeling very raw and exposed. I'm trying to get past that, and acknowledge that this is just someone that is a good enough person to let me know he's there, and is deserving of the trust he was given when he was told.
When I got over my initial reaction, I simply asked how he knew, because, after all, it's what I wanted to know most. (Please tell me I didn't run screaming down a hallway, or anything else that would make me never want to leave the house again!) He told me it was the eyes. I think he was referring to that 1000 yard stare we all know and loathe. And my mood changed. That was all. Nothing dramatic or embarrassing that will land me on YouTube. And now that I've had a chance to think about it, I'm really glad he asked. I have a really hard time letting anyone know when I'm having a hard time, and he made that act of reaching out a lesser distance to travel.
I know it probably feels like you're in a catch 22 - Damned whether you say anything or not. I liked what Amethyst said - be her quiet supporter, learn what she needs, and what approach to take with her. My only addition to that would be, when the timing is right, to let her know you're there. If and when she wants to reach out, it might make the distance a bit shorter.
