The only way to really tell if it amniotic fluid is to have her lay down for an hour(on her back/side) and then when she gets up if it trinkles down again, then she should give L&D a call, if not, then it's not amniotic fluid it's the normal vaginal discharge that comes from pregnancy! TMI I know, but I have recently been having alot of vaginal discharge, and they say that it could be from reaching the 20 week mark, you get incressed vaginal discharge. Not sure why but that's what I have read! BTW I'm between 23 and 24 weeks along as well..
I agree with amberd. Also I have heard that amniotic fluid has a sweet smell to it.
I'm sorry I don't have an answer for you as to what it is but she does need to go back in to L&D to be checked.