Nicole Alvarez, Dr. Murray's Baby Mama -- I'm Ready for My Close-Up!!!!

There's no bigger stage for an aspiring actress than the Conrad Murray manslaughhter trial -- and today, the doc's 29-year-old baby mama is NAILING her biggest audition ever!!!

Nicole Alvarez -- a former Vegas stripper Murray met in 2005 -- is flashing her BIG, GIANT, er, smile on the stand right now ... and during her testimony, she's proved she's got some serious emotional RANGE!!!

Just check out the pics below -- think she'll get a gig out of this???