Parents taxes filing rejected when daughter did not check box for someone else claim her

I was filing my daugher's taxes for the first time.  She is a 19 year old full-time student in college.  I forgot to check the box for "another taxpayer can claim her on their tax return."  I filed her taxes and they were accepted.  I went to file taxes for me and my wife and they were rejected because we tried to claim her as a dependent.  The exact message is:  

IND-517-01 - A Dependent SSN in the return must not be the same as the Primary or Spouse SSN on another return where 'PrimaryClaimAsDependentInd' or 'SpouseClaimAsDependentInd' is not checked.

I realize I can file amend my daughter's taxes but is it still true you can't do this electronically?  It has to be mailed and it may take 16 weeks?  I guess I could lose the $500 tax credit and just file and not claiming her.  I would hate to lose that.  Are there any other options?  I am receiving a pretty nice return even without her tax credit so I would hate to file an extension and wait up to 4 months!