That screenshot does not show that your account is now the owner of the data. You still have effective permissions residing from the upper level. In order to get rid of those, click on the advanced button then click on permissions and remove the first checkbox (inherited rights stuff). Copy the rights.
This means that this folder now has a seperate rights/rules/permissions set. After that you need to take ownership, not just add a user, but actually take ownership of the folder!
If the mrs account is a member of the local administrators group, it should be now problem to take ownership.
Did you see this window when you took ownership?