Put the income that is reported on the 1042-S in the area for 1099-R for retirement plans.
If she is under age 59 1/2 use code "1" in Box 7. If she is over 59 1/2 use code "7" in Box 7.
The 1042-S should have the EIN of the payer as well as information about withholding, if any, and it should go in the areas marked for that on 1099-R.
The box numbers won't match, but do your best to place the income numbers and other information in the properly labeled areas.
This should allow you to still e-file. Keep that 1042-S somewhere easily accessible in case th IRS asks for proof of any withholding, which does sometimes happen when you report it this way.