She's gone crazy. Annabelle is normally a very lovey-dovey girl towards you, but something today snapped.

"DARLIN'!! COME BACK-!! WHY ARE YA' RUNNIN' FROM ME?! DON'CHA LOVE ME-!?!?"

She shouted as she chased you down the road, her six shooter in hand. This is after you started walking away from her due to her pulling you aside from the fields you work on and interrogating you regarding a female farmhand of all people you talked too.