There is no option to show that it was split on the return.
On the 1040 just enter the K-1 as you normally would only enter the amounts that would have been entered for while she was alive.
So the capital gain would be nothing on the 1040 as all would be on the 1041. Just make sure if nothing is entered for a box, then you do not click on the tax box in TurboTax.
If you file by mail, you could attach an explanation then if you want to.
Then what is not reported on the 1040 goes on the 1041.
The year some one passes away the 1099's will not match the return so this is common.
i would not do subtractions on either return. Just make sure the k-1 is 100% reported between the 1040 & 1041.