Dude, I'm not even a woman and the first time I stepped out into Connaught Place in New Delhi, I was swarmed by an army of brown people. My first thought was "Oh shit, pickpocket attack." Instead it turned out they were all just curious and being friendly and asked questions.
And yes, I can attest to be something of a tourist attraction then myself -- fair-haired and about 198cm tall, I had people passing cameras around wanting to take selfies with me. A lot.
I'm not trying to dismiss your gf's experience as something threatening, because I wasn't there. And I know that situations can be different for women than for men. But what you described here sounds precisely like what I experienced ... as a dude ... only for me to later figure out that the threat was a lot more perceived than real. (I had a lot of other anecdotal evidence to suggest I wasn't under threat as an aside.)