The root cause of your Mother-In-Law problems is often hidden deep in her unconscious. In her eyes, there is nothing wrong with her behaviour.
Your Mother-In-Law may feel (consciously or not) like you have stolen her son. She is no longer the most important woman is his life. You have replaced her. She may be operating from a place of scarcity, rather than feeling like there is enough of his love/time/attention to go around. She may repeatedly test her son’s loyalty, forcing him to choose between her way of doing things and yours. Your husband is in a lose-lose situation, and is repeatedly set up to fail. All the worse for him if you do the same thing by repeatedly asking him to choose between his wife and his mother.
Even the most intelligent and emotionally balanced parents feel some sense of loss when a child leaves the home permanently. The Mother-In-Law has to redefine her relationship with her son, as well as make room for a new relationship with you. She may initially try to ‘train’ you in family ways/customs/recipes. But if you try to change a family tradition or take your husband to your family events instead, then you are being selfish and he is being disloyal.
Even the best in-law relationships experience some of this competition for loyalty. Depression, addiction, illness, divorce, religious/ethnic differences and financial woes can all make the situation much much worse. Don’t forget that she was also a Daughter-In-Law, and her relationship with her MIL will color your relationship. Perhaps discussing this past relationship with her could shed light on your situation – not solve it – but help you understand the root causes of her behaviour.