You're welcome to your own feelings and thoughts, and as you've said, it's not like you approached her and shamed her.
I'm an on again/off again smoker, I stop during pregnancies but there are certainly 'moments' where I cave, and regardless of what people deem 'acceptable', to me they're necessary in a way.
Sometimes I experience the most intense anxiety/panic attacks that I feel like I can't breathe, and medication, talk therapy, CBT etc doesn't necessarily kick in. Every once an a while, it actually take a few drags of a cigarette for me to feel like I can 'breathe' - I know it's ridiculous and counter-productive in a way, but it works. It forces me to sit, in silence, and to take a few deep breaths and recalibrate. It's not ideal, it's not healthy, and I'm aware of it, but in extreme circumstances, it works.
I remember being pregnant with my first child, late into the pregnancy so obviously 'visibly pregnant' and I'd chosen a far away 'designated' smokers spot to have a smoke, and this woman took it upon herself to beeline right into the area just to have a go at me, a full mouthful about her rights not to inhale my 'disgusting habit' and whatnot, just full of spiteful vitriol, when she could've simply avoided the designated area entirely. My uncle had just killed himself, and I found myself in a downward spiral and couldn't focus or breathe and was just in a complete panic and an 'emergency' smoke was the one thing, at the time, that could calm me. She didn't help. All I could think was how miserable she must be to be filled with so much hatred and anger so early into the day, at a complete stranger, at a situation she had complete control over, but she chose to come and bring me down a 'peg or two' according to her doctrine.
By all means, feel disgust, judge away, but it doesn't always need to be voiced (an I acknowledge that OP has clarified that they didn't) but fuck.. it's rough sometimes. I do wonder how some people cope with it on a daily basis..
I won't even start on the person who gave me a lecture on getting drunk at my engagement party which it turned out I was already pregnant for because I'd been 'trying' - despite her not being aware that I'd spent the last 18yrs being told I was infertile so my 'trying' was an attempt to humour my DH when he wouldn't believe me it wouldn't be as easy as in the movies..