hmmm...
I've only seen bit3h shields come up when I started approaching if I did something that merited the bit3h shield going up. Usually you can avoid if it even goes up in the first place, except in rare circumstances.
However if you think a girl has already set up her fortress, then I'd take your idea and slightly expand on it. Distance flirt with her.
Pick another HB, if you can have her be atleast as attractive as the target, if not close, and talk to her. Make sure you are within 10-15 feet of the target facing her. While you're talking to this girl, make eye contact with the target every once in a while and hold it. If you can initiate kino with the girl you're talking to even better. Making her laugh is definately a plus too. Now the target sees that you have value...you're worth more. You've suddenly become more attractive.
Now you can gauge her to see her response. You should've been reading her body language the entire time to know whether or not she's open to an approach. You can throw out tests and check for things like mirroring or body positioning. If she's not open to the approach yet, but seems to be getting there, then go find another HB and do the same thing with her. You're just adding more value to yourself by using social proof and showing this girl you can have any girl you want, you're fun, experienced, and know what you're doing.
Keep the distance flirting up and you should be able to approach soon, assuming she doesn't approach you.
I've used this method at frat parties where I couldn't approach because the girl was surrounded by like 5 guys. Her body language clearly shows she isn't interested, so I'll distance flirt and usually she'll approach me. Works wonders
Cgraz