A determined broody can be hard "to break." If not overly determined little things like putting them outside in the bright sunshine (summer) or cold temps (winter) as well as continually removing eggs & kicking them off the nest will help. Broody hens want a quiet dark place where they can nestle down. Try to give them the opposite.
Many people can break a broody by keeping her in a cage with a wire mesh floor for a few days to a week. Feed & water as normal. The idea is the air flow will come from below & cool off her belly which can reduce her urge to set. If it's a hot summer day (above 85'F), I give a cool bath (not icy cold, but not a normal warm bath) and let the hen air dry.
I've been able to stop broody hens from sitting on the nest, but it's not like they go right back to laying. Often they (my perpetual broodies) continue a reg daily routine for a couple weeks...... and then go broody again. Many times, they decide to get back at me by molting.... which also means no eggs for a while. If I stop an occasional (once a year) broody hen from nesting, then she may skip raising chicks that year. Whether I let the hen go broody or try to stop her, either way I'll be down eggs for about the same amount of time. It's not hard for me to obtain some fertile eggs, so I usually just give the hen some eggs. Since you don't have a rooster, you may want to ask some local chicken people if they can spare or sell you a few fertile eggs.
