I met Mrs Velvet (ten years now) at a party she attended with someone else. I knew the guy she came with and when I went outside to grab a smoke (quit that a few years later) I saw her there and asked her out right... "What are you doing with that asshole?". We went out the next night...
Some folks like honesty, and some folks don't. Tread lightly but it's important to NOT be emotional about it. Don't be insecure about it. At the end of the day, you don't need her, or anyone else to make it in this world. Be secure in your place in this world and it will show to everyone you hang out with, including her. If you want her to leave her current BF for you, you'll have to give her a reason why you're a better pick. You can do that subtly, by just being a cool dude who's there for her while not being taken advantage of.
Also, I met Mrs Velvet when I was 27. It's never really too late to meet your dream companion.