I think the OP was glib but i don't think she was "bragging" about how popular she was. I think the scenario you are imagining is possible, but that's not what is happening in this case. If she were consciously trying to engineer this situation, she wouldn't be surprised at the response. Of course, this could all be an elaborate ploy for more attention, but I don't think so.
And do people really think just because someone is extraverted and 'nice' that they are looking for ego validation or are "socially engineering" situations or they want something from you? Seriously?
That does underly a lot of the criticisms levelled against EXFJs here.
Now that's *my* pet peeve and it is exactly because these kind of cynical/suspicious perspectives that the OP gets the genuinely surprised and even grateful responses. I know when I encounter an unexpectedly sympathetic/nice person I'm grateful and I have a positive view of them/the experience. It's the idea of "random acts of kindness" particularly from strangers.
And there are SO MANY HATERS in the world it is genuinely refreshing and appreciated when someone doesn't fall into that mindset/attitude and is [any one of the following -] optimistic, cheerful, engaged, guileless, etc.
Not everything and everyone has a sinister hidden agenda. I think in situations like the OP's the answer lies more heavily in two directions - either conscious manipulation like in Marmalade's example or else in genuine cluelessness/obliviousness. And outside of outright manipulation/hidden agendas at play, social interactions are so nuanced that your final judgement call of it reflects more of your own mindset and temperament.