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Well, if the fish is not eating anymore, there is nothing you can do. You can't forcefeed it.
This is why it is generally agreed among dwarf cichlid keepers that secondary tanks to separate fish when social pressure and stress arises are a good thing to have.
Stress is the No. 1 killer of dwarf cichlids. Be it environmental or social stress. At one point they stop feeding, usually after the dominant fish keep them from feeding anyway. So I would not say your fish is starving itself, and the word "bullying" is out of place. It must have been going on for several weeks at least, before a fish retreats and shuts down like yours. Sadly many people start keeping them without being able to read the behaviour, so things like in your case here are bound to happen. Many of us have had such a situation early on in their time of keeping dwarf cichlids. It's learning the hard way.
So look forward. This fish is very likely beyond saving (you could try in a separate tank but I will not give it much of a chance) so once it starts going into critical state (loss of buoyancy and coordination), put it down, will you? For the future you are warned, that when a fish is retreating and being pushed into a corner and/or the surface area constantly it's time to act and move it.