I feel a little better about Shelly. Tumors are common in turtles and can often be mistaken for pregnancy. By the description of what she looked like in the past few weeks - i.e. the red veins and puffy skin - she would have had a tumor.
I was blaming myself for the past day and a half, thinking that it was my fault and that I should have been able to save her. But apparently there's nothing that can be done short of a three hundred dollar operation that isn't guaranteed to save her life.
The best I can do is be okay with the fact that I kept her in a good environment and that she was and will be forever loved.

Love.