If it's just torn fins, a few days should be fine. But, nothing wrong with doing as Jayloo does though :) Some females bounce back quicker than others, so keep that in mind.. you will be able to judge how she is in the next day or two (while in isolation/hospital tank). No need for medication, just keep a watchful eye is all.
If you are feeding primarily BBS having 2 hatcheries going at once is ideal - set up one the morning before you will start feeding, then the second one you set up the morning you do start feeding.. keep them 24hrs apart, that way you have one hatched each morning. You can feed from the same hatch for that full day - it takes a day or two before the BBS get too big/less nutritious, so just hatch enough to feed 3-4 feedings that day (you will find the right amount - the eggs are so tiny so you don't need a whole lot).
To grow them big enough for adult bettas to eat takes a lot, and isn't easy - most BBS tend to die before bigger than a pin head.
You will want to make sure to rinse off the BBS when you go to feed.. everyone has their own way to do it. Some use shrimp nets under a faucet, I personally will rubber band a coffee filter over a cup (make a "bowl" into the cup to hold the water in), use a turkey baster to dip to the bottom of the bottle and suck up the BBS (after removing the airline/stone and letting the BBS settle - a flashlight laying on the side facing the bottle helps to get them into one spot).. I then slowly squeeze the BBS into the coffee filter and then let it settle for a few mins.. takes a bit for the water to drain out, but this way I know I'm not losing any BBS through the net. Then I just take some tank water and pour a tiny bit over the BBS once or twice.. once the water drains out I then use an eye dropper (cheap at Walmart pharmacy) to gather the BBS and drip them in different locations within the tank to make sure all the fry see them.
Or can use a turkey baster, suck them up, squeeze them into the shrimp net and gently pour water over them for a quicker way.
Either way works.
But you want to rinse them off so you don't add any AQ salt into the tank with the fry.
So 2 hatcheries going 24hrs apart is all you need. Keep in mind, some fry may be too small for the BBS - most don't start feeding the fry BBS until they are about 3-5 days past their egg sacs.. they either feed a micro culture (micro worms, banana worms, vinegar eels, water worms) or infusoria for the first few days, then start on BBS once the fry are a tiny bit bigger.. can continue to feed the micro cultures up until 6 weeks or so along with BBS.
BBS can also cause swim bladder issues in some fry many believe - so many like to mix up the feedings, while others feed nothing but BBS with little to no problems. So you can judge what works best for you and yours.
What do you plan to feed them once they get a bit bigger, around the 6+ week mark?