I don't recall the specific incident, but if she indeed defies gravity without any kind of aircraft or means of propulsion, then yeah, pretty much. The thing about gravity is that it sucks, all the time. You can't just decide to make it not apply to you, and if Pinkie is able to do that, then clearly Equestrian gravity works rather differently than ours.
Pinkie routinely hold herself stationary in the air for several seconds at a time by suspending herself on the edge of the screen. For example, during
Giggle at the Ghostie at :22 :25 :56 1:02 1:04 and 1:09. She rotuinely demonstrates both
Medium Awareness as well as the ability to interact with the medium.
Pinkie also routinely demonstrates other apparent physics-defying feats:
Offscreen Teleportation,
eating significant fractions of her boldy volume within a few video frames,
Hammerspace, etc. And like mentioned just a few pages ago, Pinkie apparently has Hammerspace access to technology that doesn't otherwise exist in the verse, such as her
bicycle/helicopter.
For a recent example, watch the picnic scene of season 2 episode 3 from approximately 12:54 to 13:00. Pinkie is on her back on the ground laughing, Twilight turns her head, and Pinkie is standing on the far side of the picnic blanket. These are not animation errors. Pinkie does stuff like this all the time, and some of is so
subtle that I've occassionally noticed Pinkie Pie fourth wall events only because I was freezeframe pausing the video to get a screen capture. For example, in season 2 episode 1, when Discord takes Twilight back in time in a visibly distorted apparently invisible state, Pinkie Pie looks directly at them as soon as they arrive, blinks, and then looks forward along with everyone else. Pinkie saw Discord and Twilight, reacted to them, but
chose to ignore them and not inform anypony else of their presence.
There are
many theories to explain this, but I don't think blaming it on Equestrian physics is the answer.
You can't just decide to make it not apply to you
As I've mentioned previously, my personal theory is that Celestia is an ascended spiritual being who's created the MLP universe to give her unascended pet Twilight Sparkle a world and physical body to play in. The whole thing is a charade for Twilight's personal benefit. Some of the characters, like Pinkie Pie and Discord, are also ascended beings like Celestia, probably friends of hers, and they play along with the charade because it's fun. They're not bound by physical law anymore than an actor on a stage is bound by the legal fictions of a script they're reading. Other ponies are generally either conscious entities similar to Twilight, or artificial constructs created by Celestia to populate the world.
Probably not what the writers intended. But it does explain just about everything that's happened in the show.