Big? Is she Reddish color (as opposed to greenish)? Most likely a big girl. Check for nuptial pads, I bet you won't find them.
We have an assortment of toads that visit our toad light every night, my favorites are the girls. They are much more tolerant of being picked up and inspected.... Less likely to pee.
We have one little male tho that has somehow learned to hop, or climb, up 2 normal size stairs (brick with a concrete lip) and hunts on our porch. I have yet to see him do it, no small feat for a toad. My kids call him "Spidertoad".
Do you want to keep her in an enclosure, as a pet? If not, she will disappear in the breeding season and may or may not return. We have one large female that returns every year. She was a rehab that we kept for a while after she was accidentally stepped on. We call her "squishy". She's a big old girl and I think her breeding days are over since she hasn't left our yard for a couple years.
if you do decide to keep her as a pet, the care sheet is a good guide. As far as "stressing" her, in my experience with American toads, they are probably the toughest, most resilient critters that you can put in a box. Not to say you can't stress one, just saying that just asking shows you have what it takes to keep one happy. I've had many of them that were in very bad shape. Toads that needed to be picked up, medicated, force fed, etc for weeks on end that never lost their attitude and were no worse for wear the day they were released.