Pisgah has given good advice.
Both guns are excellent choices,, but they are totally different in how they will feel.
Basically,,, if you carry them a lot & shoot them only a little,, then the light LCR is the way to go. If you carry them a little, & shoot them a lot,, the SP is the way to go.
The difference in their weight directly relates to how they feel when carried & when shooting. Heavier guns absorb recoil easier,, and lighter guns carry easier.
One big thing is that they should fit YOUR hand. Now,, if the two of y'all plan to use the same firearm,, then a compromise in grip selection might be in order. The LCR currently only has 2 options,, but both of those seem to feel the same. (One has harder material to house the Crimson Trace laser,) but the SP-101 has many aftermarket grip options. How it fits the hands also affects how felt recoil will be.
One good note is that practice ammo can be used in all 3,, 38 spl,, but if you do go with the LCR,, you can not use 357 mag ammo like the SP or your GP.
If at all possible,, find a way to test fire each one before choosing. That means both of y'all. I'd lean heavily toward whatever your wife is most comfortable with!