My female friend has a problem........plz help?

My female friend, Denise has a little problem at work. She is a bi and she likes a female co-worker of her. It was like love at first sight for her and she really like this co-worker of her. By the way, the co-worker name is Judy. She thinks Judy like her back too because Judy has tried to flirt with her and look at her in those way. In addition, Judy loves to grab and touch Denise on her hand and waist. My friend Denise offer Judy a ride after work to the bus stop more than a few times and Judy took the offer but with a male co-worker. They have been alone in the car once and the conversation are just everyday conversation so my friend is really confused rather Judy likes her back or not. Can anyone give her some opinions? Thanks!!!