That is some major, major bruising going on. How deep is her water? Was she kept dry for several hours before you got her? I usually see this on very heavy females that are kept in a dry enclosure with no padding during transport. They bang around so much that they bruise up the plastron.

It would be a good idea to let a qualified vet look at her, if there's one in your area. That bruising could lead to shell rot if not watched carefully.

Katrina
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1.2 Eastern Muds - Fred, Ethel, Edith
0.1 Iguana - Tiffel
Foster turtles: More than I'd like the husband to know about.