Leave a path of petals casually strewn about the floor leading to the beautiful bouquet laying on her pillow.

or

stick the things in a vase and leave it on the counter.

or

leave the flowers in the common area and your card/note in her sleeping room where she will find it after she's already reemed you out for buying the flowers and will melt at the kind words from you.

What do you think is your best chance? BE BRAVE.