Spouse filed separately but we need to file jointly

My wife filed separately but we need to file jointly.  I have yet to file.  Should I;

1. File separately, then amend one return.
2. File jointly then amend her return (if this is even possible).
3. Don't file, only amend hers to jointly.

Regardless, it looks like I'll be filing an extension, how does this affect the situation?

Thank you