Democratic gubernatorial candidate Barbara Buono will tap Milly Silva, a Hispanic female labor union leader, as her running mate next week, sources say. Silva, vice president of SEIU 1199, which represents 7,000 nursing home workers in 74 facilities, will be be Buono's pick for lieutenant governor, according to three sources familiar with the decision who requested anonymity because they are not authorized to discuss internal deliberations. The announcement is expected to come on Monday.