Good morning
@Harun
It sounds like she may be broody also and that is a another thing separate from worms.
Dealing with the worms is your first priority so let's address that. If one chicken has- assume all have, you just don't know it yet. Good you have Safeguard, do you have a syringe? The standard recommended dose- wish
@dawg53 left that tidbit of dosing info- "Dose would be 0.23 ml per pound for 5 days" so an average 5lb chicken will need 1.20 mils directly dosed into her mouth. BUT, you have to dose her in a way that she does not asperate so divide your dose up into 1/4s and let her swallow in between. You will need to do this to every chicken for 3-5 days. Then repeat in 10 days.
Some people dose their chickens by putting it on their food, same 0.23 dosing applies be sure they get their dose.
IF you choose to do the (unrecommended) water method as I have been doing, it's 3 mils per gallon. Mix a gallon and dispense. I only put 1/2 gallon in my waterers at a time and remix and refill during the day when/if needed. This is also a 3-5 day repeat again with the 3-5 dose in 10 days.
If you are not planning on letting your hen hatch eggs you will need to "break her" of her broodiness. If you do plan to let her sit, she will be fine with treatment.
If you can, I have found it helpful to offer chooks some yogurt for their bellies after I'm done treating for worms to help restore their gut flora. Any yogurt or probiotic is a treat.
Good luck, glad you reached out, you got this!