Forget dressing up! It's what she has going on beneath those fancy clothes that will be the real giveaway. You can tell she's super into you if she puts effort into buying new underwear for you. You can just tell when something is brand new. The colors are bright, the lace is fully intact, and she'll have a look on her face like she's waiting for your reaction.
Thinking about you while she's purchasing new lingerie is a sign that she's in love with you. We don't know if you're aware, but that stuff is expensive! You wouldn't just buy it for any old date. The man has to be pretty special to warrant a shopping spree. So, enjoy all of the effort she has put in and appreciate the trouble she has gone to for you.