Your right. We don't know for sure. A quick Google search showed no images of her wearing one. Honestly I would be surprised if she has worn one in the past due to the American factor.
But she has also spent a significant amount of time in Canada for the last six years, and as you state, we don't know if she has worn one in the past or not. I am going to give her the benefit of the doubt.
In regards to the Hat and actually meeting during Remembrance weekend...seriously
In reference to the hat, I could go so many places with why she is wearing this hat...like...I don't know of any woman who at one time or another has not walked out of the house to do errands without wearing an article of clothing that doesn't belong to her boyfriend/husband [i.e. hat, sweat shirt, etc.]. Because they haven't dated for a lot, she doesn't know this is his signature hat....she forgot her hat and just picked up his because it sitting around his home, etc. So many potential reasons on why she is wearing it.
According to some source she has asked for time off from the filming of Suits, I think that is nonsense and they either aren't actually filming right now or she is not needed this weekend for filming. I would imagine that they have a filming schedule that they use [actors don't just sit by waiting to be filmed and specific scenes are filmed in a particular order] and unless its an emergency, her not showing up for work could impact the filming schedule. If she is a specific scenes with other actors, they would need to have her lines either deleted or given to other actors. And if she is key to a specific scene [say a scene with her love interest Mike], they would need to reschedule the shooting entirely. I have read various sources that either they have finished filming for season 6 [the 2nd part which airs in early 2017] or they haven't started season 7, which isn't scheduled to air until the summer. And since Harry should be starting his tour in the Caribbean and they know they will not be able to see each for at least a week...why not now. Who know what she has planned when he comes back.
Why shouldn't' Harry's girlfriend stay with him while she is visiting. Neither of them have anything to hide. Why stay at your boyfriend's parents home, whom you have never met...that's kind of rude and presumptuous.....and they aren't even there...and he doesn't live there. Why stay in a hotel....so we can get shots of Harry coming and going...imagine if there are overnight stays. At least in the confines of KP, there are no pics being taken and they can have abit of privacy.