Check goodwill.
Yes, much of their stock is not "interview worthy"....but at $5, can you afford not to look for the one suit that is interview worthy?
I would have 3 suggestions on the attire:
1) Shoes - I immediately notice if she's struggling to stay on her heels - so wear something you can walk professionally in (and comfortable enough to take a company wide tour)
2) Skirt - somewhere around knee length. i don't really know all the "inches above the knee" rules, but too short is a no-no.
3) Cleavage - none.
You mention "dress sweater". I'm having a tough time answering that - if it's to replace a jacket, I'd skip it. I keep typing and deleting - so I'll leave it at "i just don't know about the sweater".
Good luck! :)