Thank you for your explanation.
In your original posting you did not mention the fact that girlfriend made the will for him. You need to suggest to your father that he ask a probate attorney to examine the will to make sure it expresses his true intentions and to see if it meets all legal requirements of his state (is it witnessed by the proper number of witnesses?, etc.). The will should be what HE wants, not what girlfriend wants. Is it possible that he wanted his children to share in some of his assets, or are there not much assets to be concerned about to begin with and he doesn't mind girlfriend getting what she is getting? The fact that he mentions the safety deposit box in the will but has also designated you as a beneficiary or co-owner on the account card is a little bit problematic, although your father probably didn't realize it. The beneficiary designation will override the will and the safety deposit box contents will be yours, no matter what the will says, and you can visit the bank safety deposit vault right now to ask them about their policies/procedures to confirm that this is in fact the case.
If you don't want your father to change the beneficiary designation with the safety deposit box to name the girlfriend as beneficiary of that, then maybe you don't want the lawyer to discuss the contents of the will if you want to leave things as they are with YOUR name as beneficiary of that.