37 weeks!!! prego!!!?

my sister is 37 weeks going to be 38 weeks on thursday! we are sooo excited. but my question is..yesterday she called me and said that she thought her water broke and she was having some servere to moderate contractions (not regular, some were every 4 min and some where 30-40 mins apart), so i picked her up and took her to the hospital..any way it ended up that is was her mucus plug coming out and they tested her for any water leakage and none:( lol. they checked her cervix and she was like 1 1/2cm. the nurse said it still could be awhile, but i wanted to know from ur experiences how long to u think it'll be??