In the episode entitled Dream On Jessie encourages Rachel to make her dream come true and find her mum because Bryan Ryan, Mr Shue's nemesis from when he was at the school, tells the glee club that their dreams will not come true. They look through Rachels old baby things and Jessie plants a tape into a box. We see Jessie get into a car. Shelby Corcoran (Vocal Adrenaline's coach) is in the driver seat and at the start of Jessie and Shelby's conversation we get the impression it is a ploy to ruin New Directions, however when Jessie asks why she doesn't "just go up to her and say hi my names Shelby, I'm your mom" and Shelby explains that she signed a contract that means she's not allowed to contact Rachel until she's 18 and that Rachel has to find her. On the tape Rachel's mum is singing. Rachel sings along with Shelby and this is their first duet.
In the next episode (Theatricality) Rachel, Mercedes and Quinn spy on Vocal Adrenaline and Rachel hears Shelby sing Funny Girl. Rachel (who has up until this moment been telling Quinn and Mercedes that she would be doing exactly what Shelby is doing/singing) immediately recognises the voice, stands up walks to Shelby and says "Miss Corcoran, I'm Rachel Berry, I'm your daughter".