I'm not a student, so my apologies in advance if this information is completely useless to you, but...
South Bend itself is very conservative. It's got a very midwestern farm town vibe to it, IMO. I live in Detroit, used to live in Chicago and go back to Chicago a lot, so I tend to go through that area about once every couple of months. FWIW, I'm not a lesbian, but I feel uncomfortable whenever we stop around there, just because of having a few visible tattoos and a more artsy/intellectual look. South Bend is just very homogeneous.
As far as the Catholic element of the school itself, that might not be as much of a problem. I go to a Jesuit school in Detroit, and I know that my school has a lot of resources. A lot of Catholic universities advocate community involvement (and in some cases, community activism) which tends to encourage more of an atmosphere of diversity and tolerance IMO.
You'd be about ninety minutes from Chicago, which has a thriving gay and lesbian community, so if there weren't ample resources in South Bend, you'd at least have easy access to Chicago. The Metra also goes between South Bend and Chicago, although it stops running somewhat early. If you're interested, you can check out the route here:
http://www.nictd.com/service/dailywestbound.htm