Does she have dual citizenship or is she just a Canadian citizen?
Yes and no. She has due nationality of a sort. BUT It's complicated. AFAIK, China does not permit dual nationality. As such, she can't be Chinese and Canadian at the same time!
BUT because she is a Hong Kong (HK) citizen by birth, or by having lived in the territory for more than 7 years, she is entitled to HK ID Card. which then lead to being classified as a HK citizen.
As a HK citizen, she is entitled to a Chinese national overseas pasport (exactly like the BNO). And just like the BNO, we can't enter China proper without further document like a VISA.
So as you can see, she is not really a dual national, as she can't enter China proper. But she is dual national with HK. that is to say she is HK and Canadian citizen. (not Chinese and Canadian citizen).
As such, she can and does speak about HK affairs as can I. (I'm exactly in the same position but British instead of Canadian).
Now, here's the crucial difference, whereas I became British because of my parents. (I was a kid). Whereas most of these scums from HK became Canadian by chioce at just before the hand over for hatred of CCP, so they all use their money and influence to "flee" HK.
In reality, most stayed in HK because they were making too much money from HK to totally abandon it! but still maintain the security of fleeing if the "worse"does come!
So while they enjoyed the fruites of HK, they started to plot for change! This groups of people are usually rich and powerful like Jimmy Lai, doctors, judges, lawyers and "pro-democracy" politicians.
This is why, some politicians (usually pro-China) are now openly arguing for that no politicians can hold a foreign passport. In other word, they can't cause trouble, and then upsticks and leave!