I know how hard it is to let an oportunity slip and all the "what if's" you will have to deal with if you do not act now, so this is what I would do if I were in your place. It's also what I should have done 6 years ago if I knew about PUA back then...
First off, forget the "let her know we will be going as more than just friends" stuff. That puts way too much pressure. Ask her for that thing, and either go as friends and escalate there, or escalate in the meantime and use that oportunity to consolidate your position.
Your game plan shoud be simple: instead of luch ask her for something else, a night out, a drink after work, a concert, whatever. If it helps, pick a place with sofas, great to do some kino, unlike tables wich pretty much just get in the way. Isolate. Escalate.
This is the best escalation guide I know, so here you go:
majik-s-guide-to-kino-escalation-vt163160.html (kudos to Majik, by the way)
Let us know how it went.