Mr Soul - what you have is a crush on this woman.
She has noticed it, and is probably a little flattered, but that is all - she has given you absolutely no indication that she sees you as anything other than a colleague at work.
If you were to declare your 'love' for her, you will embarrass and upset her, and I am sure you don't want her last memory of you to be negative.
Attraction in the work place is perfectly normal and very common, but please don't make the mistake of seeing it for something it is not - and it is not love.
Hopefully you can simply remember this lady as a pleasant distraction, and find someone real who is willing to embark on a relationship with you.
Good luck.