Rainbow was enjoying a flight around the outside of the castle. Winging over a tower she pulled her wings in, twisting as she fell. Opening her wings up again she easily caught herself and smiled at the simple stunt.
She was aware of a wailing sound as it moved through part of the castle nearby. Twilight hadn't caught her niece yet. If she took any longer Rainbow figured she'd offer her help. Her speed should let her catch the little tyke in not time flat.
A pink blur caught her peripheral just before something slammed into her. Years of training let Rainbow catch herself before she even lost a foot in altitude as well as bringing her arms up to grab what had hit her. Looking directly into the almost comically oversized wing of the foal they were foalsitting let her know exactly what just happened.
Annoyed at being caught off-guard like that Rainbow Dash let out a small sigh as the breeze going across her bare breasts helped soothe her. The realization that she was wearing a sports top dawned just as quickly as the foal moving to latch onto a nipple.
Shaking her head Rainbow said "Now Flurry. You can't just divebomb into someone when they're flying like that. You also shouldn't just help yourself to their tits."
Flurry Heart, having found no milk to sate her hunger, tried to push off of the flying mare but found that Rainbow had a very secure grip. Powering her horn she quickly teleported several feet away and into a window.
Rainbow Dash glided over to that window, folding her wings as she neared and came to a perfect landing on the floor inside. Looking down at her exposed breasts she contemplated leaving them as such. Though any stallion and several mares who see her like that would likely go into awesomeness overload, like Soarin that time she and Spitfire teased him for a week straight before he 'caught' them having fun.
Chuckling to herself as she pulled the halter back down to cover herself, thinking how he'll never be able to look at a weather vane the same way. She then proceeded down the hallway to help her friend catch the flighty foal.