Wait, what? You signalled you wanted to ask her out, she said she had a boyfriend, and... I guess this is when you told her you're poly, she said she's not... Maybe I'm missing something here, and granted, I'm not poly, but I hardly see why this calls for a formal discussion of boundaries, any more than her saying she wasn't interested in dating you but would like to keep being friends would.
I myself have never had a notable interest in someone already in a relationship, so I guess I don't know what it's like. All I know is watching the first two seasons of Smallville and wanting to throttle Clark until he straight-up asked Lana to dump the jock for him already.
('Course, he knew for a fact the guy was a dick...)
She's known I'm poly since one of our first few conversations. I have a polyamory symbol tattooed on my left ring finger.
She asked me about it and what it meant, so I told her. Telling someone I'm poly right after asking them out and being told their involved with someone tends to come off as "I'm cool with it if you cheat on him," and that is not a good idea even if it was the case. Which, I'm not, or dishonesty in general for that matter.
The issue of boundaries is very important. What friendship is and is not distinct, especially not for me. My various friendships have included everything typical of romantic relationships, and the distinction between friendship and romantic relationship tends to be more about choosing how to define a relationship more than actual substance.
While monos typically have more of a distinction between romance and friendship, there is variation. For some it's as simple as "no sex" or "no falling in love/expressing feelings of love," or both. On the other end, some feel it's inappropriate to have opposite-sex friends at all and tolerate it if their partner insists on it, and plenty of things in between.
I have a general idea of what sorts of things are and are not okay, but there are some things I'm unclear on. She's hugged me before. Was that okay in the first place? Is it not okay now? Can I hug her or do I have to wait for her to hug me. Can we hug whenever we want or should we limit it to only every once in a while? Can I touch her affectionately in other ways as long as they're not overtly sexual? Some of these things come naturally to me and I need to know if I'm likely to cross the line without realizing it.
There's also the opposite of that. I would assume that I'm not allowed to kiss her. However, it's possible that they would think it's okay as long as we're not making out, and that quick, closed-mouth kisses are fine. If that's the case, I would probably like to do that at some point.
The emotional boundaries are even less clear cut. It's known that I'm attracted to her and like her, apparently that's okay as long as I don't act on it. What if I eventually fall in love with her? is that a problem, or only if I act on it? What does "acting on it" mean? Can I say "I love you" to her?
Most of that was just examples of why it's important, a lot of it isn't relevant now and I'll wait until it is. Right now it's mostly about communication. So far I've agreed to not act on any romantic feelings I may have, to not try to convince her to let me act on those feelings, and to not give in if she tries either of those things. She has agreed to bring any concerns about me to my attention, and to ask me questions before making assumptions. These kinds of things are necessary because I know from plenty of experience that stupid bullshit gets in the way very easily but can be avoided if everyone pays attention, and if the arrangement isn't going to work I'll catch on quicker and can possibly back away before I become too attached to her.
It's a good thing you don't live in my country, I can't imagine that a guy your age peppily discussing boundaries would get much.
What? Someone questioning my appeal to women? This has never happened before. I am confused and hurt by this. Seriously, this is going to take some time to sort out. There may be crying.