Um...no. Here's what will happen. Former girlfriend will claim money. Estate will claim money. Insurance company, who is willing to pay money, does not know who gets it under law. They will throw it into a pot called "impleader". Everyone gets to talk to the judge who will decide who gets it. He is not going to decide a former girlfriend who has no claim other than that the deceased wanted to take care of his wife has many rights to the money. It has happened in wills, but I have not done a search for beneficiaries. If someone gives me more than "that's what he said" I might research more. Until then, I can't see a judge awarding it to an ex with no relationship and no long-term monetary issues between the two. (Which are why the facts are important.)
Bottom line is that those who think the beneficiary designation is IT, period, are wrong.