That behaviour usualy means the fish is stressed or bored.
Adding another female might prevent her from becoming bored but it would make her (and the newcomer) more stressed as they may well end up fighting over hierarchy.
If you can find a three-spot female (it's actualy better you get one of a different color - ie: not a gold but a blue or an opaline or a lavender for example) of the same size and first re-arange the tank a little to confuse the girl you have right now, you may be able to itnroduce the new fish without any serious aggression and they should afterwards both settle down.
Having said that, I'd personaly suggest you stick with the single female - at least for the time being. If she doesn't calm down, you can always add another female later if you take care to re-arange the tank or isolate this female for a while before adding the new one.
Just in case, check that none of the other fish in your tank are voerly-active and that the upper layers of the tank are free for the gold to use (ie: no overly-boisterous fish constantly swimming at the top of the tank). Consider adding some floating plants and/or very tall rooted plants and perhaps some other tall ornaments to break up the tank and make the gourami feal more at home. Also try feeding some live foods more often to make the gourami's life a little more exciting. You may find that she benefits from having a mirror placed by the tank occasionaly (but only for relatively short periods). You may have seen/heard of this being done with male bettas. Male three-spots often react in a similar way to bettas and females may at least feal they have some companionship if you do this ocne in a while. Don't over-do it though - it can sometimes prove stressful if they start 'attacking' their reflection (though females won't usualy do this).
