You can use TT to calculate the penalty and add it to your balance due or you can just pay the calculated tax and let the IRS bill you for the penalty.
If she filed last year, she may be eligible for a penalty exception, so having TT do the form (2210) is recommended.
In TT enter at:
Federal Taxes (Personal in H&B version)
Other Tax Situations
Additional Tax Payments
Underpayment Penalties
