I hate to be a negative Nancy here, but if she isn't interested, this may make it really awkward for her to come into your place of business again. I suggest asking her outside of work, not while making her Carmel cappuccino.
Tell her you know of a place (if you do) that has even better coffee.... and ask her if she would like to accompany you sometime. Or... You can simply say. "Would you like to have dinner with me sometime?" or lunch...etc
offer her a drink and sit next to her and have a little conversation let her know how your personality is and after tell her you would like to take her out to dinner but just take things slow don't rush things make her feel like she's not being rushed or forced into anything. Goodluck!