I'm just guessing that your Indy is bonded to you and that her screaming is a kind of protest against your boyfriend being with you, or something :S I'm no pro, but I bet someone more experienced will give you some answers, they use to be pretty fast on these forums
When I first got my pionus she would scream when my boyfriend talked, but she no longer does it. I think the reason lied with him and not with her, he was first of all not acting properly around her. Since he started doing that, she calmed down a lot. Second, he has a very intense way of being, when he's speaking he's talking just as much with his hands and arms as he is with his voice, and his voice is rather penetrating. He has what you would call a "high energy", so even before I got Penny I often had to tell him to slow down because when he gets started he speaks faster and faster, and louder and louder (not meant in a negative way, he just gets very excited, haha). I don't know if your boyfriend is the same, but if he is, try telling him to think of
how he's speaking. When my boyfriend learnt to calm down and keep both a slower pace and a lower, more consistant volume, Penny has completely stopped "interrupting" him. Also, it's much more pleasing to the ear for me, hehe, so I'm glad I've got her to "force" him to calm down