My sister in law is a great person to me

My sister in law Ava is great person to me and we have a great relationship. First time I met her, she saw I would treat my wife right and proved it to her well. Says I am the only one that works on her vehicles to this day. Saw I am a great auto mechanic and it started when I saw an estimate from another shop she took her car to. I checked it over and only needed one part, said I saved her a lot of money that day. Another one was the front brakes needed replaced, an ex boyfriend of hers whom was not mechanically inclined said he would do it. Knew not to let him do and I did them. She has brought me new customers, one is her friend Valarie lately. Found out she was going to another shop whom was screwing her and now goes to me for her car repairs.