Compliments should always be genuine, but most of all the opposite of what she expects to hear. If it's a drop dead gorgeous, you compliment the personality, etc. The lesbians are not used to being complimented for their looks, as they're mostly plain girls, some prettier than others. If she's really beautiful, no need to compliment her looks, compliment her style or personality, but it must be genuine. You can't game her much at her place of work, try to find out where she goes out and appear there one day. Talk won't get you far. You need to be somewhere out, where you can relax, dance, have a few drinks and you can unleash your masculine desire upon her lol
This is a long shot, you know that your self, she's in a relationship and a lesbian too.
But any chance you have, in my opinion, is when you get her somewhere away from her girl, relaxed and in the mood to party. Only then can you escalate physically, like you would with any other chick. She needs to feel she turns you on, the more physical you get, the better, and you can't do that if you're not in a club or a bar without looking creepy.
BUT the point is, even lesbians have a weak spot for masculine energy. Even if we love our women, we're not immune and we sometimes crave this big masculine man who will protect us and be all manly and bigger than us, it's just sexy and it's natural, the more macho you can be and give us honest, sexual attention, the easier we'll cave in. You have to understand lesbians are not used to being chosen by attractive males over other girls that are available.
If she can feel your sexual desire in a non-creepy way, that's your best shot.