Final answer:
Tina would most likely be diagnosed with Bipolar II disorder as her symptoms of excessive cheerfulness, talking too fast, interrupting others, excessive spending during elated times, and feeling sad and guilt-ridden align with the characteristic manic and depressive episodes of Bipolar II disorder.
Step-by-step explanation:
Tina would most likely be diagnosed with Bipolar II disorder. Bipolar disorder is characterized by dramatic shifts in energy and mood, often affecting the individual's ability to carry out day-to-day tasks. These shifts can include periods of elevated or irritable mood, known as manic episodes, and periods of depressed mood, known as depressive episodes. Tina's excessive cheerfulness, talking too fast, interrupting others, and excessive spending during these elated times are indicative of manic episodes. The description of Tina being mostly sad and guilt-ridden at other times aligns with depressive episodes. The presence of both manic and depressive episodes is characteristic of Bipolar II disorder.