do you have to be invited to hangout on frat bid day?

It’s an open invite for all girls, Greek or not. The way it goes is that typically you go w/only one frat’s bid day (early morning start partying before going down the steps on campus, then partying after the steps too). Girls can and sometimes do go to two diff frats’ bid days, but you’d have to plan out your day and Uber around a lot, and order shirts from each frat to wear too,
bc they all don’t typically like it if you’re wearing another frats shirt while you’re at their party

(Most girls there are actually in Greek life, but there are plenty that go who aren’t because it’s open to all girls, even if they don’t go to TAMU)
The only kind of “invite” is a Facebook invite to the FB page where the frat will just have details of their plans for bid day and the link to order their bid day shirt, so you can have one and wear it by the time bid day starts.