That's the thing that I wasn't totally clear about. I knew that being out at school (handholding, etc.) was one of her boundaries, and I knowingly crossed that boundary. The reason isn't so much that she's uncomfortable with us being out at school, though she's not comfortable with that, but it's that i work in the building where her department is housed, and i work with S. Her friend that saw us together works in that building also, and many of L's professors and colleagues either have offices or teach classes in this building. So it's not just a matter of her not wanting "people" to know, but of her not wanting to jeopardize her professional and academic career because her colleagues are uncomfortable with her lifestyle choices.
L does have complete veto power; she and S are friends and get along famously, so she hasn't felt like she's had to use it, which is good, because I think that things will work out, it's just a question of going back to basics and making sure everyone is REALLY on the same page before we continue rather than just barging ahead and assuming.
I have embarked on a policy of complete and total honesty, which i think will serve us all well in the long run. I don't want to cause any more hurt or distrust between us, because she doesn't deserve that. I love her more than i've ever loved anyone, which is why i married her, and I appreciate so much that she's willing to take this journey with me. And i know i've done a lot of wrong things in starting this out the way I did, but i'm working on rectifying the situation and making it mutually agreeable to all three of us -- and i know that open and honest communication is really the only way to do that.