[COLOR=333333]Hello there and welcome to BYC! [/COLOR][COLOR=333333]

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If you are seeing a lot of blood in the poop, then coccidiosis is no doubt the cause. You would want to get some Corid (Amprolium) from the feed store. It is used for 5 to 7 days and will take care of cocci.
When and how often you worm really depends on a few things....you clean your facilities are, how many birds you have, if they free range, if you have added new birds from unknown sources to your flock recently. And it also depends on what you are worming with. I have had great luck with Safeguard Liquid Goat Wormer. It takes care of most all worms in the birds body with the exception of a few species of tapeworms. Tapes are not all that common. Valbazen will take care of every worm then have. Once or twice a year is good for free ranged birds or birds kept in crowded spaces.
You might also post this in our emergency section for more help with your hen as well...
https://www.backyardchickens.com/f/10/emergencies-diseases-injuries-and-cures
Don't wait too long if you are seeing blood in the stool. Cocci can kill fast. So can an impaction of worms.
Good luck and I hope you can get her back to good health soon.