My 20 month old has been a dream since she was 4 weeks old going to bed and sleeping all night!!! She has recently become a big sister and after about a week of us being home with the baby every time she gets put to bed she screams, sometimes it can last few minutes or she can get in a real state and not settle for hours. I have tried for the past 6/7 weeks and it’s so distressing to hearing her panic every night when I lower her into the cot 
once she is asleep she doesn’t make a peep all night ... I am at a loss on what to do !!!! does anyone have any advice