It is possible that:
* You might have misremembered the name. It's easy to get names confused, especially with a series as complex as Harry Potter.
* You might be thinking of a fan-created character. There are many fans who create their own characters and stories within the Harry Potter universe.
* You might be thinking of a character from another fictional work. There are many characters named Lucy or Violet, but there is no known connection to the Snape family or the Harry Potter series.
If you can provide any more information, such as:
* The book or source where you saw this name.
* Any other details about the character.
* What you remember about them.
I may be able to help you identify the character you're thinking of.