There is this movie scene that was always stuck in my head. I remember a nurse or somebody giving an old lady pills to take, but when they would leave, the old lady would take out them out of her mouth and put them in a bag. Towards the end of the move I think, or somewhere in the movie, the old lady gets the bag, which is now filled with the pills she didn't take, swallows them all to commit suicide. That's all I remember.

Beautiful (2000)
Wikipedia synopsis:
Mona Hibbard (Minnie Driver) is a young woman from a troubled home who has one overarching goal: to become the winner of the Miss American Miss pageant. Unfortunately for Mona, women with children are not eligible for the crown, and she has a young daughter (Hallie Kate Eisenberg), but her best friend Ruby Stilwell (Joey Lauren Adams) selflessly agrees to raise Vanessa as her own daughter. As Mona gets closer to winning the title, she has to come to terms with her troubled past, her thoughtless present, the fact that Vanessa is starting to clue in to her true parentage, and an ambitious reporter who is thrilled at the prospect of becoming a TV star by humiliating the despised Mona.

Her friend, Ruby, is a nurse or some sort of aide at a nursing home. As I recall, an elderly woman does just as you describe. They accuse Ruby of murdering her, and her arrest causes problems in their setup. It's been quite a while since I've seen it, but I think that memory is certain because it made me think of Rosemary stashing pills to use later (on someone else, though) in "Rosemary's Baby".