I don't think it's too Catholic at all. At least in the Church I think of it as a hymn more than as a name. In any case it's really beautiful and has a lovely vintage feel, but it's known enough that I don't think anyone would have trouble with it.
Gloria Alyona
Gloria Claire
Gloria Giselle
Gloria Isabel
Gloria Judith
Gloria Leonie
Gloria Merryn
Gloria Rosalind
Gloria Shoshana
Gloria Tanith
Gloria Winifred