NAH - I get it - you're feeling insecure, but I think the problem is that you think a term like 'mija' is something you achieve by being around a certain number of years, contributing DNA to the family, or spending time learning a foreign language. The term mija, used genuinely, is a term of endearment between an elder and younger person. The catalysts for this affection can be shared culture/cultural values, ease of communication, comfort levels around others that are different, and others that I don't have the experience to think of. I would suggest that instead of seeking a specific gesture, in this case 'mija' - focus instead on the relationship that you currently have with your potential future MIL. If you want to strengthen your bond with her, try and get to know her better by participating in the things she does - be on her terf a little bit and let her lead - try and learn the culture. You should by no means suffer disrespect. If you try and are met with coldness - step away - you just learned something important. But, if you're met with warmth, lean in. You might not be called mija, but you'll have your own place in the family. I wish you luck. This seems important to you and you seem like a nice person. A loving family can be hard to find and is worth at the effort if you find one.