PLEASE PLEASE PLEASE put her back within 100 yards of where you found Her! Like on the other side of the road - the one it was crossing towards. They have VERY specific territories and moving her will likely cause her to die - either through starvation or not finding a proper shelter come winter. Moving her also risks taking any disease or parasites from her population into a new one.
IF she is gravid she will hold onto the eggs and has a high chance at egg binding - in my experience they often need to be chemically induced to lay their eggs when in captivity. Also, the babies will imprint on were they hatch and stay within a few acres of that site for their entire lives...just release her
I know it's hard to think about them crossing roads, but it is her home and he knows where all the food, shelters, mates, etc are. I've worked with turtle conservation and relocation in school and in wildlife rehab - relocation protocol takes years, and even then many don't survive - and that is with help from scientists and conservationists. Just tossing her in a new location is comparable to dumping a dog out into the wilderness, except the dog has the chance of someone finding and rescuing it.
Just google turtle relocation and read some of the articles - that and taking them for pets are causing the populations to drop off rapidly. If you want to help just escort her back to where you found her ASAP and put her on the side of the road she was trying to get to.
No cage is too large - nature is the best template - a snoot can't be booped too much