There is no official patron saint for homosexuals. Some people argue that St. Sergius and St. Bacchus had a homosexual relationship and therefore its argued they should be the patron saint of homosexuals. The historical support for their relationship though is scant coming from one historical revisionist John Boswell.
I think the poet Gerard Manley Hopkins S.J. would be a good patron saint of homosexuals as an example of someone who worked through and battled those desires.
Just be there for her, show her the love of Christ, but do be firm in Catholic teaching. Help her understand the teaching. Try to find a good blog and stories like this one: