This has the unpleasant aroma of rumors being shared about you behind your back.
She just happens to be a very self-righteous WT automaton who deems it her duty to treat you as marked, judged and sentenced with the spiritual capital punishment of shunning.
You've been deemed contaminated and infectious and so she shuns you like a leper.
Here's a shunning antidote:
The best response is to go out of your way to be in her face with pleasant conversation starters every single time you can get within speaking distance of her, and if she's to far to hear you then make friendly gestures of hello, wave madly like you like her a ton, and if she's out of sight, tell others how much you like her and that you're best buddies and just about soul-mates.
This way the coals you're heaping upon her head will burn with the intensity of the fires of Gehenna.
Be happy, be merry and make her life a living hell through kindness. She will hardly be able to withstand the shunning antidote.