In 2013, the AGI floor for someone under age 65 is 10% of AGI. The 7.5% floor applies to those 65 or older. Since it is you, and not your mom, who is taking the deduction, you must use the 10%-of-AGI floor.
Test for determining deductibility of IRA deductions. Active participants in employer retirement plans are subject to IRA deduction phase-out rules if adjusted gross income exceeds certain threshold.