Have you ever humped a mortar base plate, radio and extra batteries, all your crap and a few mortar rounds up and other anything?
Your wife may be great with a shovel. Women can get strong, but basic is only about 9 weeks long and another aprox 4 weeks for Infantry AIT.
Biological differences may not be insurmountable, but time is perish. No point spending time where you don't need to.
I am now a training developer for the Military, time is something we have very little of and have to make the best us of it as possible.
Mortar base plate? No.
SATCOM radio, spare batteries, weapons, ammo, explosives, and two weeks' worth of gear? Oh, yes.
It should probably be borne in mind that most people don't just up and enllist - it is
a commitment, and not something that should be entered into lightly (it's not like getting a part-time job.)
Most people who really do want to enlist usually have thought about it for some time - and taken the time to prepare for it. If they haven't, they deserve to wash out of training.
Honestly, I don't think anyone
should enlist with the idea of "getting fit" - and training should reflect that. PFTs are public information and readily accessible (moreso than when you or I signed up!) and if you can't meet the PFTs, you should not be accepted.
Does this sound Draconian? I offer no apology. As I said earlier, signing up for the Armed Forces isn't like getting a job somewhere - and military training should focus on military matters. Take the time to get into shape - whoever you are - before you ship to Basic.