If she files for her own benefit and if you were born before Jan 2, 1954, you may file a restricted application that allows you to draw a spousal benefit of 50% of her PIA while your benefits accrues delayed retirement credits at 8% per year up to age 70 when you’d switch to your benefit. But your spouse must file for her benefit first.
When you switch to your benefit at 70 she will receive the greater of her benefit or 50% of your PIA. The PIA is the benefit you would receive if you began at your Full Retirement Age.
If you pre-decease her she will switch to your benefit if she has at least attained her Full Retirement Age. If she had not attained her FRA and elects to begin the survivor benefit, it will be reduced by about .067% per month begun early.