Android - How to stream music from one android device to another?

This app could do the trick:

Bluetooth Music Player Free

You need to install it on both Android devices and pair them. Then put the tablet in ListenMUSIC over Blueetooth mode and the the phone in shareMUSIC over Bluetooth mode.

Apart from "Bluetooth music player" (mentioned in above answer), you may also try SoundSeeder speaker or SoundSeeder Music player. As i remember, at first you should pair the devices. From the description of SoundSeeder Music player:

Soundseeder turns all your devices into into wireless speakers. Play your music louder and share it with your friends. All connected devices (Android, Windows, Linux, Raspberry Pi, ...) play the music in sync as one large sound system.

SoundSeeder speaker is

a speaker-only version of the SoundSeeder Music Player and was designed for devices running Android 2.2 - 4.0 only.