Does she say “no, it does that”? What does this mean? Thanks

Her phone is buzzing/vibrating (there's no tone/music, so you wouldn't normally say 'ringing') - "Do you need to get that" ("Do you need to take that phonecall/respond to that text message?") "No. Uh, no. It does that" (I do not need to, my phone just sometimes vibrates randomly) "Yeah, mine too".

“It does that” That’s a thing that happens and there’s not much you can do about it

Think of it this way, and maybe it'll help explain the humor in it a little bit: 1. A dog growls 2. First person says, "Is he growling at something?" 3. Second person says, "No, he does that." It's obvious the dog is growling at something, and both people know that, but the second person is just kind of nonchalant as if that just happens randomly. Same thing with the phone vibrating.