Move the betta her to her own small tank. Any time you put a betta with other fish you need to be prepared to move it to it's own home if things don't work out in the community. Get her a 2.5g or 5g and use a bit of filter media or some filter squeezings from the main tank to cycle it.
As someone else asked - what type of plecos are they? If they are common plecos then yes you are very overstocked. If they are a smaller variety then no you are not. How long has it been set up and did you cycle it before you added the fish? If not you are going to have to monitor your water parameters very closely and do water changes because you will get alot of ammonia with that many fish.
And yeah - what's up with the lights? They do look EXACTLY like I would imagine a tin foil hat to look!