There isn't a specific symbol for sister in Scottish Gaelic, unlike some other languages.
However, there are some traditional Gaelic symbols that might be associated with sisterhood:
* The knot: Knots are often used in Celtic symbolism to represent connection and strength, and could symbolize the bond between sisters.
* The willow tree: Willow trees are often associated with femininity and sorrow, and could represent the emotional connection between sisters.
* The heart: A heart, in its simplest form, could be used to represent the love and affection between sisters.
It's important to note that these are just interpretations and there isn't a definitive answer for a specific symbol representing sisterhood in Scottish Gaelic.