I have a similar issue…a slight squeaking at low speeds coming from the passenger side of the vehicle. The key thing is it happens while NOT braking….which leads me to believe that a simple pad replacement would not resolve the issue.

Just like you said, when I hit the brakes lightly (like just enough to turn the brake lights on...maybe a little harder), it gets louder. But, normal braking gets rid of the sound all together, and this started for me last summer AFTER I changed brake pads and rotors.

I have wasted over 120 bucks to get rotors resurfaced and pads greased, but it's still there. Without the radio on I hear it when just cruising slowly and it’s driving me insane.