Dreams often reflect our subconscious thoughts, feelings, and experiences. In your dream, several key elements stand out that may offer insight into your current emotional state and relationships.

1. Alumni Auction and Jennifer: Attending the alumni auction could symbolize a revisiting of past relationships or experiences. The presence of Jennifer, who has a complicated history with you, might suggest unresolved feelings or thoughts about your past connections. The fact that she is now a lesbian and still has an interest in you could represent your own feelings about friendship versus romantic interest and the complexities that can arise in relationships.
2. The Date: When you express that you like Jennifer in a platonic way, it highlights themes of boundaries and expectations in relationships. Her reaction may indicate anxieties about not meeting others' expectations or fears of rejection, both yours and hers. Ending the date abruptly could symbolize a desire to avoid uncomfortable situations or conversations.
3. Chocolate Cherry Bundt Cake: Taking the cake could represent indulgence or coping mechanisms. It might suggest you are seeking comfort or pleasure, especially since you feel guilty about your girlfriend. This may reflect inner conflict regarding your current relationship and the choices you're making.
4. Thrift Shop: The thrift shop with expensive and unattractive items may signify feelings of disappointment or dissatisfaction with your current circumstances or choices. It could represent a search for value or meaning in your life that feels frustrating or unfulfilling.

Overall, this dream seems to highlight themes of relationship dynamics, feelings of guilt, and a search for personal fulfillment. You might want to reflect on your current relationships and consider how they align with your feelings and expectations. It could also be an opportunity to explore any unresolved emotions from your past that may be influencing your present.