How to delete a class object inside the same class using inside a method?

Let's say I want to implement the following functionality.

I have a class Employee, which has 3 variables viz, name age and salary. I will override the __add__ and use it to create a single object that will be a combination of the two objects used. For example, if I have A and B, and if I do A + B, I want their information to be combined. I am able to do it. But now I want to delete one of the objects, let's say B, so that there won't exist that B Employee in the system. I tried using del, but I can still print its values after deletion.

class Employee:
    __slots__ = ['__name', '__age', '__salary']

    def __init__(self, name, age, salary):
        self.__name = name
        self.__age = age
        self.__salary = salary

    def display(self):
        print(f"\nName: {self.__name}")
        print(f"Age: {self.__age}")
        print(f"Salary: {self.__salary}")
    
    def __add__(self, other):
        finalName = f"{self.__name} & {other.__name}"
        finalAge = (self.__age + other.__age) / 2
        finalSalary = self.__salary + other.__salary
        del other
        return Employee(finalName, finalAge, finalSalary)

    
a = Employee("A", 22, 10000)
b = Employee("B", 25, 15000)

a.display()
b.display()

# Prints as expected
Name: A
Age: 22
Salary: 10000

Name: B
Age: 25
Salary: 15000

a = a + b

a.display()
# Additon operations takes place successfully and it prints the following

Name: A & B
Age: 23.5
Salary: 25000

b.display()

# Actual Behaviour
Name: B
Age: 25
Salary: 15000

# Expected Behaviour
Some error saying B does not exist or not defined