User blog comment:SpookyBoogie27/Light Novel Spoilers/@comment-99.120.77.79-20140127000033/@comment-16281343-20140127001008

I don't think that is possible. Even though Valerie has 3 Holy Grails, that is still treated as one SG. "Judging from their words, even having just one of them will be capable of making it reach the Balance Breaker."

So, if one reaches BB, all of them will.