I'ld advise you to protect your heart. Women are pretty good at picking up when a guy is really into them. It's not normal for a woman in a relationship to be meeting up with another guy for lunch and coffee. Think about it: If you were involved with a woman - like in a relationship - how would you feel, if you discovered she was meeting some guy for coffee, supposedly just to be friends.

"All's fair in love and war", so if you can win her away from some other guy she's dating, I'ld say, "Go for it." On the other hand, platonic friendships between a single guy and a woman in a relationship usually just lead to the guy getting frustrated. There's been lots of threads on that topic here on this forum. Watch out that you're not being used. Seems like she asks a lot of questions and may just be pumping you for what workplace info she can get out of you. I'ld strongly encourage you to try and meet other, more available, young women.