"मैं इसे नहीं देखूँगी।"

But it can mean "I will not see him" and "I will not see this/it" as well. Remember that personal pronouns in Hindi only vary with respect to number (यह vs ये) and proximity (यह vs वह), not gender.

The quirk about मैं यह नहीं देखूँगी। vs मैं इसे नहीं देखूँगी। though is that if the object of the sentence is a human, it has to be in the oblique case; a non-human object can be in either case (इसे is the oblique form of यह).

So, while मैं इसे नहीं देखूँगी। can mean "I won't see him/her/this/it", मैं यह नहीं देखूँगी। cannot mean "I won't see him/her".

Edit: इसे is the accusative of the oblique form of यह.

I would say "मैं उसे नहीं देखूँगी" or "मैं उस को नहीं देखूँगी"