You and your friends twilight, Applejack, fluttershy, rarity, rainbowdash and pinkie pie all were invited to the wedding of shining armor and princess cadence

But this Candace was a fake Candace being the Queen of the changelings pretending to princess cadence to feed off the love Candace had for shining armor

The fake cadence locked you and twilight sparkle in the caves of canterlot as your prison as the wedding happened after Twilight used her magic to break a crystal wall it revealed the real Candace who was imprisoned like you two

Cadence: "w-wait don't hurt me!...twilight.. It's me!"