Romans 12:21 - Do not be overcome by evil, but overcome evil with good.
One thing that my own mother taught me was that if you confront someone unflinchingly yet with courtesy and respect, they have little choice but to comply.
Once I was complaining about a neighbor kid who played his music too loud late into the night. She said to just go ask him nicely to turn it down. So I did. Amazingly, it worked. I realized that if I'd have yelled over the fence, it would have given him permission to yell back and crank it up. But by asking him nicely, I put him in a position where he would have been in the wrong to do anything but turn it down. I only had to do that a couple of times until he got the message.
Perhaps the best thing you can do is say, "Mom, I love you and I know you don't approve. But this is what's going to happen and I'd really like it if you'd just accept it. Can you do that for me?"
That last sentence, btw, is callrd the "closing". In sales you always "close" the deal by asking them out-right to agree. Once they've done that, it's hard to back out.
