Dreams about gift-giving, especially within family dynamics, can often reflect underlying feelings about relationships, expectations, and self-worth. In your dream, your sister's disappointment with your gift of pens may symbolize a fear of not meeting others' expectations or feeling inadequate in your ability to please those you care about. The fact that she asked you to fill your dad's stocking with her vast collection of pens could suggest that you feel a sense of responsibility to fulfill the roles expected of you within your family.

The multitude of pens might represent the overwhelming pressure to meet various demands, both from yourself and others. The different colors of the pens could symbolize the variety of emotions or qualities you associate with your relationships—perhaps you feel a mix of responsibility, anxiety, and a desire to be appreciated.

Consider reflecting on your current relationship with your sister. Are there any unspoken expectations or pressures affecting how you interact? This dream might be encouraging you to communicate more openly with her about your feelings and the importance of understanding each other’s needs and desires.

Lastly, the recurring thought about whether the store knew how many pens were purchased could indicate a concern about how well you understand those around you or their expectations. It may be a prompt to consider how you gauge the needs and desires of others in your life.

In summary, this dream suggests an exploration of familial expectations, feelings of inadequacy, and the importance of communication within relationships. It may be beneficial to have a conversation with your sister about your feelings and perceptions to strengthen your bond.