Is voltage divider output affected by load resistance?
If you put a load (= a resistor) in parallel with the 'lower' resistor of your voltage divider the output voltage will indeed be lower. Did anything lead you to believe it would be otherwise?

Let's say your load resistor is 100K too. It is in parallel with the 100K resistor of the divider, so together they are effectively a 50K resistor. The total circuit now consist of a 100K resistor and a 50K resistor, so the output voltage will be 1/3 of the input.