that's an easy fix. The top of the line is curved but the bottom will allow you to run a block off of it at a 45 degree angle. THAT is how you'll get your line back with filler. Let it define itself. Hopefully the top isn't too curved so you can angle it less than 45 degrees and run it off the bodyline, but if not use tape to sand the top. Then sand on the body line last.
check out this video at the 4 min mark. Watch the part where I blade in filler on a bodyline and how I sand it. Again, not the greatest example.
this technique works REALLY WELL on bodylines and especially curved wheel well bodylines without worrying about what they'll look like in primer. It's works so good you don't have to use surface cleaner to check to see what it will look like in primer cause you KNOW it's gonna be good.