How to answer when you are confessed without hurting others?

If you refuse directly and decisively, the injury is inevitable, and the problem becomes how to minimize the injury.

This must be quick. The longer you wait, the more she thinks you are the default.

And you have a girlfriend, you don't have to tell her, just say you don't have feelings for her.

Why should we deal with this problem quickly?

It means that long pain is better than short pain. And quick and decisive, her chances of breaking up with you are low.

Don't be shy, it's better for you to express your true thoughts. Not answering clearly, or hesitating, will only delay her and herself.