Goofy, semi-lewd version of my previous post. (Not sure if this counts as completely suggestive, but it’s intentionally moreso than the original)
 
Maybe Applejack was reminded of something from the past. Maybe she secretly likes the idea of her girlfriend being her sugar-momma. Maybe Rarity is her sugar-momma, maybe she likes to be called that in private…. Maybe it’s a cute and innocent tease she encourages, or maybe she really is a giant mom-dom. Who knows? Either way, you get the impression that Applejack’s NEVER going to admit why such a random slip like this would happen.
 

 
Would you believe the idea for this version actually came first? XD