That's kinda weird that she values her boyfriend so much but spent an entire day with another guy and as you said "was interested and did kino with you" and even made it to your room for one on one time and you ALMOST got a kiss. I dunno man, first you say that she is interested and you figured you would get it for sure (so your initial impression was all sign were go) and then you say "it seems to me that her personality isn't like that." You're kinda contradicting your self right there. But whatever. I still dont' think her bf was much of an issue here, based on everythign you've said thus far.
However, if you're really just wanting to find out, this is pretty simple man. How about "are you single?" lol. You can look at her kinda suspiciously when you ask her this, with a smirk on your face, so it's kinda cute and bold at the same time. This is much different than "sooo, uhmmmm, do you ahve a boyfriendd?" which a lot of guys do. And then don't make it a big deal when she says yes or no, (and hell, if you're still getting the IOIs, then proceeding when she says "no" can actually even score you some points on her scale, in terms of boldness and confidence and self belief, but not everyone can pull this off or has enough game and "not give a damn" attitude). Quite simply, a lot of girls are not really all that serious about their boyfriends, some just have a guy not to be alone, some don't really like him or resent him for whatever reason and are looking for ways to "get back at him", some run all over their doormat bfs and have ZERO respect for them, some are just promiscuous little cvnts that will do you if you game 'em up enough and build attraction, ETC ETC ETC.
This is the exact reason I told you that you "may not want to know" in your particular situation. Bottom line is, if you are gonna screen all of them, then you will find out that about 75-80% of chicks that you end up talking to you will immediately have to disqualify because of the bf "issue". The reason is, hot chicks don't really stay single/alone. (I'm assuming you're talking to hot or at least good looking girls). How many hot chicks do you know that are just straight up single? Not too many I would guess. They would rather be with someone even if that person is not ideal for them. Most of these really hot girls come with all sorts of issues .. FINE stands for Freaked out, Insecure, Neurotic, and Emotional LOL. I usually deal with hella fine girls, but I'm not gonna lie, they are usually a lot more headache. The girls that are a little more "normal" looking are on average more secure and confident in them selves (kinda ironic right? lol go figure) and have other things going for them.
The hot chicks look good on your arm, but they're usually a lot of headache to deal with. They rely on their looks so much that when their looks start to fade, so does their entire sense of self. It's kinda scary, but that's what a lot of us are signing up for lol. But yeah, not to go off topic too much, these girls are rarely if ever really "single". They usually are either with some dude, or dating some dude, or something. Usually they are insecure so they would rather be with a dude that they are not even really that into than be with no one. Hence, you'll be eliminating a lot of girls that don't even care about the dude they are "dating" and that you can potentially bed (mannn, this sounds damn bad when typing it out lol, but I just have to be honest). It is what it is man, and if you want to eliminate them, than that's fine with me. Go with the "are you single" route (with the confident, suspicious look on your face and a slight smirk, and not making it a big deal if they say "yes", just proceed as normal, unfazed, and take the lead).
And yes, NEVER be awkward! lol Make sure you work on your body language and being congruent all the way through. Sometimes that can mess guys up when trying to "close" a girl, they get a little nervous and their body language changes and she senses that you may not be the confident/alpha male that she was feeling attractions for. If your body language and how you cary your self, tone of voice, changes to that of a weak man, this may be sending her to run for the hills also. Incongruency can kill attraction. Pretty much, she finds out you were just putting up a front. Anyway, just my two cents.