IMO yes and no, yes it is an indicator of interest, but no, in as much as it’s not intended to be seen as such. People tend to go to extremes when trying to hide something. Much like little kids are so afraid of their classmates figuring out that they like so and so, rather than just being neutral, they take their behavior to the polar opposite and pick on the person, or tease them. As adults the methods might be a little more subtle but at the root we tend to do the same thing.
Basically it’s like this…
If she only said goodbye to you, or at least only you consistently (you and person A on monday, you and person B on tuesday etc.) then yeah people might figure out you have her attention in a special way and she knows this.
If she was neutral and either said goodbye to nobody, said goodbye to everyone including you, or said goodbye to a few people at random with no particular pattern, then nobody would be the wiser. However…insecurity (since she likely thinks you’re not interested) could be causing her to go a bit further to the other end of the spectrum…ie saying goodbye to everyone BUT you.
She threw some ioi’s but you distanced yourself. So she figures you’re not interested and A continuing to show interest is a waste of time, and B. this is a big one, continuing to show interest could make her look desperate. Women are so used to being the ones pursued that they usually don’t expect that when they take a little initiative and pursue, that they’ll be rejected. Done infrequently it can increase a woman’s interest but done too firmly and solidly and she’ll pull back. Any further action risks more emotional hurt, plus on an instinctive level she might feel that seeing her rejected by a man she shows obvious interest in will make other men less likely to accept her.
I mean think about it, if you are even slightly interested in a woman, but it’s very clear she’s into a different guy, but that guy rejects her and shows obvious signs of disinterest, how would your opinion of her change if you watched her continue to chase this guy and show obvious indicators of attraction toward him only to be shot down day after day?
What’s more, if the girl finally did decide to go ahead and date you instead, how secure could you feel that she’s with you because she wants to be, and not because she’s settling for what she can get, instead of what she actually wants? Would you be worried that if the other guy changed his mind and decided he wanted her that she would drop you for him at the first opportunity?
This is what she’s trying to avoid. Chasing game that’s too difficult hurts her chances with other more willing males in the long run.