Did David make Louise crazy?

I'm not sure if this has been mentioned before, but just bear with me. Before David, Louise had no prior mental illnesses. It seemed like he just tossed her aside but kept coming back, making everything worse. If he never came back, she may have been completely fine. She was really, truly in love, and that loss of love is hard to get over. Not to mention, the death of Mrs. Graham probably brought her budding schizophrenia to full fruition. To make matters worse, after David told Louise that he wasn't ready to get married, making excuses because he no longer loved her, he decides to pursue Mr. Graham's daughter, Carol. He could have been after the money, like Louise conjectured, or maybe he subconsciously wanted to torture Louise. What did Carol have that Louise didn't have, aside from being younger and richer? The main point of the movie is that Louise went crazy over David, but maybe, just maybe, it was David and not Louise that spurred this string of events. He was always there, always coming back. Following his first encounter with Louise after coming back, didn't he think that maybe he shouldn't stick around? If he only stayed to work, why was it so important for him to go to Mr. Graham instead of them meeting somewhere (unless that was part of their work situation), and why did he come to the wedding when no one invited him?