problem with 2 broody chickens... advice needed!!!!

For the past 11 days my bantam has been sitting on eggs..... everything going great until this morning...

another chicken has also decided to go broody... she waited until my bantam left the nest box to eat and drink, which
she does every morning.. and took over her eggs, and wont let her back on..... do I remove the new broody so the bantam can
re sit or do I leave her on the stolen nest.... or another option do I go buy some more fertile eggs and let her sit her own??

Im concerned if I take her off the eggs and put her on some new ones she may just leave them, and as the other eggs only have 10
days left its far to late to put newly brought eggs under the bantam!!! any ideas what I should do.... im worried if i interver they may both leave the nest and the
eggs will go cold and the chicks will die????