SeismicMilk

But Blossomforth first appeared as a toy in G4. She was a recolored Rainbow Dash with shy eyes, muted colors, and no freckles. And then she appeared on the show as a white pegasus with a different mane style, brighter colors, round eyes, and freckles. Hasbro has a big lack of communication in regards to character designs (mostly mane and coat colors) and, occasionally, names (ie: Flowerwishes, Roseluck, etc instead of their names on the show) but they don't have a tendency to start throwing out random Alicorns like they have ponies, especially on the infant toys.

I think that Skyla is the daughter of Candence and Shining Armor. Even if there isn't a very long gap between seasons according to the show's timeline, keep in mind that an Alicorn's growth is accelerated. From the time that Princess Luna was changed from Nightmare Moon to the time she visited during Nightmare Night, her stature had gone from smaller than Cadence to almost as large as Celestia. Alicorns are also much taller than normal ponies anyway. I hope that she's their daughter. She looks like a cutie and it would be adorable to have a baby Alicorn.