I actually tried to figure out the same, and their is a way I found. Jump up top to the ledge above with the poison and get on the very edge of the platform, as you actually don't get hit there. Grab the rose as soon as she is not looking and then book it to follow behind her. When she reaches the stairs she turns around immediately so jump over her when she reaches them. Then because you are above her she doesn't see you and also doesn't follow you up the stairs.