There aren't really any women associated with the Hiberno-Scottish Mission (the period of Irish/Scottish missionary work that began with Saint Columba).

There are a great deal of Irish holy women during this period (though some of them might be pagan goddesses Christianized into saints) but few left Ireland, and those that did usually only made it as far as England or various small British islands. Saint Modwenna - an Irish-born, English saint - is said to have made a pilgrimage to Rome though.

The closest example (that I know of) of an Irish holy woman who traveled to Europe is (the likely non-historical) Saint Dymphna. The story goes that Dymphna was the daughter of a pagan Irish king and his beautiful wife. After his wife died, the inconsolable king sent messengers all around in an attempt to find a new wife as beautiful as the one he lost but, no matter how far and wide they looked, his messengers could find only one woman who matched his dead wife's beauty: his own daughter.

When the king tried to force his daughter to marry him, Dymphna fled with her confessor to Antwerp, and then settled in the town of Geel, where they founded a church and hospice for the poor and sick. Eventually her father tracked her down and, in a fit of madness, killed her when she refused to come back to Ireland to be his wife.

Since then Dymphna has been the patron of the mentally ill and has had a church, with a prosperous sanctuary for the mentally ill, in Geel since the 14th century.