Hey /an/ so earlier today my family and I found a Diamondback Terrapin (pic related) in our backyard. I've figured out its a female about 7 or 8 inches big. I've been reading up on care for them for the past couple of hours and I'm concerned since she might be sick. Her shell is kinda beat up and peeling on a few places and I don't know if its normal or if she's ill. So we put her in the bathtub with running water and she went straight for it. We tried feeding her lettuce and I even found a wasp with its wings missing (lucky me) in our backyard as well. She didn't eat anything though.

I left her there for about 30 minutes before I took her to my room. She immediately went off into my closet and made herself comfy in a pile of clothes in the corner. I'm thinking of keeping her and as I've said I'm reading up on care for her but I've got some questions:

Habitat:
>What is some equipment I would need for a basic tank setup? I'm on a budget at the moment so I just need the bare minimum for now. I plan on adding on later.

Filtration:
I'm thinking of keeping her in a brackish water environment since according to my readings its natural for them.
>If I buy a regular tap water filter and fill her tank with that "fresh" water mixed with some aquarium salt would that be ok? Or do I need actual fresh water?
>If I buy a filtration piece for her tank will that remove the aquarium salt? If so, what type of filter should I use that won't remove the salt?

Food:
>What brand of turtle feed should I buy?
>Would calcium blocks heal her shell from peeling?
>Is the peeling natural or is she sick?
>What kinds of plants will Diamondbacks eat?
>What kind of plants should I keep in her tank?

Thats all the questions I have at the moment. If I missed anything please let me know. Any additional advice would be greatly appreciated.