Yes, Radience looks like Celestia GET OVER IT I USE BASES.
Meta-Alicorns are born with their cutie marks, and only reveal their true form in a moment of grave danger. For Radience, it would be if her sister was ever hurt. Radience's job is to put all the sparkles of day where they go. NO SHE ISN'T ROYALTY RARITY MADE HER THE CROWNSTUFFS!! She's just a pony who lives in a space-time rift with Meiko, as does her sister Starlight.