If she kept her job in New Jersey but moved to Maryland, she'd still pay New Jersey income tax, so would not save anything.
If she took a job in Maryland then she would likely save money on income tax if the rates were as you suggest (and likely made up for by other taxes/fees). Determining the actual difference in income tax burden would be trickier to calculate, as neither state taxes all income, they will have deductions from total income to get to taxable income, and allowed deductions vary by state.
Further complicating the calculation is that both states have a progressive income tax (rate gets higher as taxable income increases) and the brackets do not line up between NJ and MD.
If her taxable income happened to be identical for both states, let's say $75,000, then she'd pay $2,651 in NJ, $3,510 in MD.
So while the marginal rate at $75,000 in NJ is 5.525% and 4.75% in MD, the effective rate is actually lower in NJ for her, MD would become more attractive as taxable income increases.
NJ 2016 Tax Brackets
MD 2016 Tax Brackets
That's all just for state income tax, local and county taxes could apply, and differences in sales tax and property tax rates would also factor in to a thorough comparison.