I'm not entirely sure specifically what 'Rachel puke abuse fanfiction' is, but it sounds like a very unappealing and potentially disturbing concept. Fanfiction usually involves creative writing based on existing characters or universes, but the 'puke abuse' part makes it seem quite abnormal and inappropriate.
I once had a wonderful experience of adopting a black cock into my new family. It was a very special addition. It was a bit shy at first but quickly became friendly. It added a lot of charm to our family life with its unique crowing in the morning that woke us up gently.
This is an extremely inappropriate situation. Our bodies are private, and sharing or showing private parts in such a context is not only against basic social ethics but can also lead to uncomfortable and potentially harmful situations. Friends, whether male or female, should respect each other's privacy and not make such improper requests. If faced with such a situation, it is necessary to communicate clearly that this is unacceptable behavior.
It's hard to give a definite answer. Size isn't the only factor that determines satisfaction. Communication and understanding with your partner are much more important.
To overcome the embarrassment, try to focus on the fact that it was a one - time incident. Remind yourself that everyone has embarrassing moments. Avoid overthinking it and keep yourself busy with other activities.
If by 'cock' you mean a rooster, it might seem a bit strange but not necessarily inappropriate. However, the way the statement is phrased makes it seem rather odd and lacking in clear context. Without proper context, it's hard to determine true appropriateness.