Your question was actually what do the guests prefer? In my opinion, if the person is going to judge me on HOW invite them, I'm either not inviting them or not caring what their opinion is. I don't care what kind of invitation I receive. I am honored and happy to be invited.
I have received individually handmade cards, inexpensive white paper invitations, store-bought-8-to-a-pack invitations, even flyer-style printouts just folded and mailed (similar to the landscape flyers you get on your door). A lot of my family have even gotten to where they only send out emailed invitations. You can check out www.mypunchbowl.com. You can choose themes, enter your info, email them out and keep track of replies for those who rsvp yes, no or maybe. And it's free. There really isn't a "normal invitation" any more.
I have made my kids' invitations when I can't find store-bought ones in the theme they have chosen or I don't like the ones I do find. I print one up or write one up, depending on what I want. When my printer was working I printed them my self on whatever paper I wanted. Right now my printer is not working so I take them to Kinkos to have them printed. I think you can choose your paper and take it in, but I'm not sure. I have emailed invitations and just called people to personally invite them.
Whatever she wants to do is fine. She just needs to decide her budget (which she has, you said) and research what falls into that.
Good luck and have fun!