Here are some antonyms for lonely:
populated
sociable
befriended
close
frequented
inhabited
loved
unlonely
Basically, by lonely I mean someone who feels lonely even in a crowd. Such people are usually depressed. They feel happy if anyone gives them some positive attention.
These people want a man in their life and they actively seek mates. Whereas a person who is comfortable in her own skin won't have to go on looking elsewhere for attention and love since they are enough for themselves.
What should I say when I have to say I want someone who is ....?