Yes they can, provided they should have 2 gallon space for each of them.. Female bettas do not fight each other like males do, so they could very well share the same tank, but half a gallon is way too small. ... If you can, go for a 1o or 15 gallons tank where you can keep 3 or 4 females together and even add a male betta.
i'd consider getting the 5 gallon so they are not cramped :3
