It's the wife's fav too. The fish seem very happy at the minute I was looking to get another to keep him company.
Currently have 6 neon tetra, 4 male guppy and a couple oto...I thought this was a better impellis??
It could be a female betta as they tend to be less colourful and with shorter fins than males. I can't tell from the photo if it's a short finned male or female. If you bought it from a chain store (Pets at Home, maidenhead Aquatics) it won't be anything other than a Betta splendens.
You could always set up another tank around 25 litres for the betta. If you take some media from the current tank and also get floating plants, it would be cycled for just one fish.
Male bettas are solitary fish which are best kept alone. Some females are as bad as males, and are also best kept alone.
If you got it from Pets at Home, together with a Molly, then my local Pets at Home tell me that you should ask to speak to the manager of your shop. They should offer to take it back, with a full refund, or give you a discount on a tank for it.