Javier met her when he sold a painting he won in a poker game in the auction house where Trish works and they have been together ever since.
Gloria seeing how close Manny and Trish get since they share lots of common interests, she is worried about being replaced. When Javier proposes to Trish, she runs upstairs and locks herself in Manny's room. Gloria tries to talk to her and she finds out that the reason Trish doesn't want to get married to Javier is because she feels like she can't live up to Gloria as a mother and as a wife.
Gloria hearing that abandons her plan to scare her away and she welcomes her to the family.