As others have said, you can’t make people like you. You can be warm, charming, kind, intelligent, witty, humorous, caring, thoughtful, attentive, organised, diligent, solvent, heroic, moral and lovable – and guess what, they still don’t like you.
So why don’t they like you, you might ask.
Maybe you have all the attributes that they secretly want. Maybe you are a threat to a particular relationship. Maybe they need something to hate or to gossip about to distract from their own frustration or shortcomings. Maybe you remind them of someone they disliked. Maybe they feel competition with anyone of the same gender. Maybe they are bored and just need an easy, albeit critical, topic of conversation. Maybe they criticise because they want to feel that their advice is needed. Maybe they have discovered criticism and guilt are effective ways to control people. Maybe they are cliquey and like to think of themselves as insiders and everyone else as outsiders. Maybe they are mean-spirited or mentally ill. Whatever it is, it isn’t caused by you. You are not to blame. (I repeat, you are not to blame.) Nor can you fix it. What you can do is be very clear about your boundaries.
If your future mother-in-law has been mean to your fiance’s previous girlfriends then it isn’t too surprising if she is mean to you. In fact, if you are a fiance and future wife, rather than merely a girlfriend, then I would guess that she is going to be even meaner because you are much more of a threat.
This is likely to continue until you and your fiance get married. Once you are married either your mother-in-law will wisely realise you are a permanent fixture and try to get on with you or she will foolishly just carry on being mean until (or if) you have children. Then she will wisely realise that if she is going to see her grandchildren she will have to be pleasant to you and obedient to your wishes or she will foolishly carry on being mean and have a very lonely old age. So, the decisions are hers to make.
What you have to do is decide what you want in the long term. Don’t think about it in terms of individual events in the past. Think about what you want over the next year, 5 years, 20 years, and think about the minimum you can expect out of the relationship.
I would suggest you go for respect. This means you and your future husband need to sit down and decide what is acceptable and what is unacceptable now. Then, if your mother-in-law does anything disrespectful he and you can jump on it immediately. It’s like dealing with a small child. You can still be honourable and pleasant but you do have to be firm and consistent.
If there are any of her other daughter-in-laws or son-in-laws with whom she is equally abrasive then make the most of it. There is strength in numbers and power in conspiratorial winks.
If people cannot be bothered to come to your wedding or cannot be bothered to be nice to you then there is no requirement for you to feel any responsibility towards them. You can fill any void with close friends – those to whom you really matter.