Yes, it is very possible -- sometimes it's even easier, since HBs are rarely being fulfilled by their boyfriends.
However, if she truly believes that she's "in love" with him, then it would be a lot harder and many (including me) would argue that it wouldn't be right to break them apart.
The idea of "boyfriend destroying" is to disqualify yourself by actually encouraging her to keep going out with him, while at the same time making her second think their relationship.
Here's an example (credits to Rye Lee):
PUA: Eh, it's alright, we would never work out anyways. I mean, ten years down the road I can totally see you guys in a nice little house with a white picket fence, 2.6 kids, and a dog.
HB: 2.6 kids?
PUA: That's the average number of kids the average family in America has. Anyways, while you were living the simple life with ___, I'd be flying from my private island off the coast of Madagascar to my estate in east London. My life would be way too hectic for you to be a part of.

HB: Well, I highly doubt that me and ___ will ever get married...
See what's happening? You're making her relationship with AFC to be boring and ordinary, while you're living the exciting life. Which one looks more appealing? You're instilling doubt in the relationship, DHVing yourself, and disqualifying all in one beautiful package.
There's a lot more to it.. search "boyfriend destroyer."
Hope I helped!