I would largely agree with
@daggermark but would not recommend any filler.
I would use the emulsion, "full fat" and push it in to bits of paint that are still loose. I would then apply another coat when dry.
Once that coat has cured I would use 180-220 grit silicone carbide paper to lightly sand the parameter flat. The new paint should "lock" the loose edge on the previous paint, Allowing you feather the edge.
Your walls have a textured finish. If you use filler, you will have a odd smooth section.
I am guessing that you only applied two coats of the new colour last time around. The paint build up is pretty minimal.