Yes, unfortunately, one row of hair is normal :S At least in that first year, Hasbro skimped on hair so ponies could either have one or two rows. My childhood MM Ivy has one, and a second hand one I found has two. same with Petal Blossom. It sucks!
As for fading, I've seen it happen a lot with G1s. I guess someone could have kept her in a place where sun was hitting her from the front and her tail was in the shade.
As for Light Heart, she is the one that came with the wedding playset (Wedding Playset with Light Heart), not to be confused with the wedding chapel with Dainty Dove.