Sorry but no, Sean is most definitely a boy's name - it's been in the top 1000 names for boys for many years, although some parents decide to use it for their daughters for whatever reason. I guess it depends on where you live... in America, giving girls boy names is very common, but in Europe and Australia it's much more of a taboo.

If it really bothers you, maybe you could change it to something similar but feminine like Seana/Shawna/Shauna? Or you could go by your middle name, or just pick your favourite girls' name and go by that :)

Good luck xx