Don’t beat yourself up, you are stronger than you think.
Your gf should know better than to allow people in the house who have it/take it, let alone those willing to wave it in front of you. TBH I’d kill anyone who did that in my house in front of my husband who is a recovering addict. I was even mad when one of his mates came over the other day and had been using, although I know he didnt do any while here, as he couldnt wait to leave after a couple of hours!
Keep on the good path! You are better than this.