I realy think you need to deal with this now before baby comes. eaisier said than done i know. try explaining to your older daughter that your other little girl is being naughty and you are going to sort it. but in the short mean time there may be some noise at bed time. better a little short burst of alot of noise, and a short period of a lack of sleep. than your older daughters sleep being disturbed for a longer period of time. which will be more damageing. then start being firm. explain to you little one before it starts what the routine is and what is expected from her. so there is no missunderstanding. when she starts leave her for five minutes. go up and tell her it's sleep time firm but calm. she will carry on crying. then leave her ten min. then twenty then thirty and so on. the porpose of this statagy is that a child learns how long it has to cry before you give in. if you keep seeing her. but always extending the time. it means you are not ignoring her but you are showing her that you mean business. if you give in you are showing that is how far she needs to go to push you. I think she is testing boundries. but by doing this you a setting her good guide lines ready for when baby comes and caos starts again. this took about 3 nights with my daughter. i found it a firm but fair method that a friend of mine used an then taught me. good luck i hope it can help.x