Sending only one finger print is a mistake. I'm curious if she took her fingerprint in the US or outside. If she did it on her own with ink, I think you might have a problem.
opening day of application - I'm sorry I have no clue what you mean here. The day the applications are opened is one day, the day they enter your application form details is another, the day the fingerprints get scanned is a third etc.
will it be mixed up with the current application - I'm a bit unclear what you mean here. However you can send multiple applications and I can assure you they will not be mixed up. This I am certain.