The only way moneywort would make a Betta bloated is if the Betta was starving and it ate a bunch of moneywort found in the tank. Rotting moneywort will contaminate the water and eventually make it toxic for any fish.
I heard that it releases stuff thats toxic to the fish. ANd my betta has been bloating; i feed him every day and fast him on sundays and the plant is in great condition
I only feed him 2 pellets in the morning and 2 at night then alternate food weekly with flakes. I fed him pea regularly on saturdays and fast him on sundays. Hes been bloated for a long time... about a month now