Then that means they go by a different name in game.
On the bottom of the screen with the action bar (the friend bar), you can search there. Find the friend you are looking for and type their name. The characters will pop up.
Another easy way is when you are sending them a gift type their name in the gift section and their "characters in game name" will show up. so you will now know who is who. then you can know who to delete.
hmm wait.. i just re-read your question. so that option won't work. (I'm leaving it there as a just in case and also if other people have the problem of searching for a person with a different name).
For you- I'd say try the settings. I know it's random and it depends on the game, but you can go to settings and look for the game and manually delete the person from the game. This keeps them on your friend list so you can still play other games with them (like if they are more active on Farmville for example but not as active on Gourmet Ranch. then you can choose to delete them from Gourmet ranch etc....)
Or ask a friend if they know they person and get their name through the grape vine and delete them then.
to delete a neighbour in facebook(3 deletes max a day) :click on neighbours, when it opens, click again on neighbours, it will then show you your neighbours with a red cross so you can delete thenm if needed.
I have a number of 'neighbors' in Knights and Brides, who don't play and have a low level (ie: 1 or 2) that were there when I started playing. Thing is I want to add neighbors that do play and I can't. The game says 'my neighbors limit is reached'. How can I add neighbors?
Clicking on Neighbors and again clicking on neighbors only shows those who are currently playing, not the sleeping neighbors. The people who make the game should correct this!!! I also checked by trying to send a gift. The same name as is on the bottom of the bar is there. This cannot be found in my neighbors. I now only have a few neighbors who are playing and lots who are sleeping. I want to delete them without all this dificulty. Please fix thsi!!!!