The other gourami won't be able to hold it's own. Seperate them, re-arrange the tank and, if the gourami being picked on is the same species as the bully and female, get a couple more girls the same size and add all three in again. Get yourself some floating plants as well while you're at it and lower the temperature (very gradualy) so that it's not above 77 deg F. If you have two males, return one and keep the other alone or get a couple of same-sized females. Again, re-arrange the tank etc before adding them.
BTW, what species of gourami is the 'other' one and how large is this tank?