send legal notice for keeping me on hold from 1.5year for marriage.

Me and my gf are in relationship from 3 yrs. We had promised each other for marriage. I am doing business from last 2 yr & she is doing her job. 1.5yr ago I told my parents & they are ready for marriage, & she also told her parents, but her father told to wait to settle my business. Now it's 2 years, I am earning good income from my business. But still her father is not convinced & asking me to do job for fixed income which I don't want to do & also my girlfriend is ok with that. It's been 1.5 year now & still me and my parents are kept on hold by her and her father for decision on marriage. Whenever I ask her for decision as we are in 30's now, she ask for more time. I have waited a lot & also gone through mental trauma due to which I lost focus from my business resulting into stress & depression bcoz of this waiting thing. So I wish to send a legal notice for wasting my time and keeping me and my parents on hold from last 1.5 year for marriage and want them to take quick decision.