Plot hole: When Lindsay brings Tru breakfast in bed on the second version of the day, she is excited that Tru remembered her birthday, and she also mentions that nobody else did. But it's still very early in the morning. It's not at all reasonable to assume that anybody forgot her birthday just because they didn't call before 8am.
Plot hole: Meredith is subjected to a random drug test at work. However, the drug test is announced late at night. Tru is already working her "graveyard shift" at the morgue, so we know the regular workday is over. Hardly anyone would be in the office. Therefore, it doesn't make sense for the company to be administering this drug test, said to be requisite for all employees, at that time.
Plot hole: Meredith submits to the drug test at her office. In the next scene, which takes place later the same evening, Harrison tells Tru that Meredith's test came back positive and she was immediately fired. But it takes at least 24 hours to get a result from a urine test at all. If the test is positive, the sample must be subjected to a more thorough examination. It usually takes at least 72 hours to get the results in that case. There's no way Meredith's positive results could have come back in less than six hours, even if a lab had been open late in the evening.
Plot hole: John is slightly surprised to find that Tru is acting as bartender for the party, but doesn't dwell on it any further once she explains that she was supplied gratis to make up for the earlier "problems" with the room. But John should actually be extremely alarmed to find her there, given that he poisoned the ice and expects the other guests to drop dead. He certainly wouldn't want any witnesses to that.