Rainbow immediately knew she said too much, the tears that began shimmering in Applejack's eyes were proof enough of this. Only her pride kept them from running down openly onto her cheeks. Instead she stared hard at Rainbow Dash, who felt her heart sink.
"Applejack..." She started to regret the fact that she hadn't simply swallowed the words, which passed through her lips only a few moments ago.
"Save it, Rainbow".
"But..."
"Ah said: save it." Interrupted Applejack; her voice now cold as stone. She turned back, starting slowly to walk towards Sweet Apple Acres. There was something incredibly painful present in her posture, as if she was seriously hurt. Her step was slow, almost forced, head down and tears still resting obviously in the corners of her eyes.
Rainbow Dash stayed in place, hovering a few meters above the ground, not sure what to do now. Applejack clearly didn't want to talk with her and she couldn't blame her. The earth ponies were always considered as the worst race of all and in the past other races often showed them a lack of respect and had a tendency to use and humiliate the earth ponies at every opportunity. They weren't treated as full-fledged citizens and their role was relegated to ensuring food and serving the pegasi and unicorns. Those times are long gone now, of course, but it was still a very painful subject, especially for ponies like Applejack, who was always proud of being who she was and would never change that. Rainbow knew she crossed the line this time. Teasing Applejack was one thing, but openly calling her race worse, even though she knew how degraded the earth ponies were in the past just because of their lack of wings or horns - it was something utterly different.
She bit her lip and started to fly toward her friend, who was almost reaching her destination by now. The outline of Sweet Apple Acres in the distance was becoming clearer and clearer.
"Applejack!" She cried out, trying to get Applejack's attention, but the mare ignored her, accelerating a pace.
Rainbow Dash landed next to her and looked at her friend's face, but Applejack's eyes were fixed straight ahead and she refused even to acknowledge Rainbow's presence.
"AJ, please!" She insisted, now standing on her hind legs and resting her fore hooves on Applejack's shoulders. "Just listen to me!"
"Why don't you just go eat dirt like every proper earth pony" Whispered Applejack.
"What?" Squeaked Rainbow, obviously taken aback by her friend's choice of words.
Applejack sighed and raised her head, looking ahead and still avoiding Rainbow's gaze as best as she could. "Those were your exact words, Rainbow Dash."
The cyan pegasus gulped. She wanted to defend herself. Turn everything into a joke. Act as if nothing happened. But she couldn't. She didn't mean it when she referred to Applejack like that, but it didn't make their argument any less real. And even though she knew that Applejack can't be mad at her forever, she simply couldn't stand the thought of letting down her best friend like that.
"I-I'll make it up to you, Applejack" Rainbow Dash whispered, her voice cracking slightly. At this point she was almost in tears.
A bittersweet smile appeared on Applejack's face. She shook her head and passed by still not looking at her pegasus friend.
"Ah don't think so, Rainbow".