I am no expert in any of this and probably shouldn't respond first, but here goes. One thing I am certain of is that blended families are tough. You can search the archives here on mamapedia and find many such discussions.
There is no "right" way for a family to blend and for a MIL to treat a step-grandchild. The important thing is to have a good understanding if your expectations and your husbands, first. The two of you need to talk and come to some agreement. As I said, having no direct experience with a blended family, I am not entirely sure it's fair to expect your MIL to treat your daughter, who would be her step granddaughter, the same as she treats her biological grandchildren. Honestly, I just think that's too much to ask. I know others feel militant about this but personally, I think it's unrealistic.
What about your childs' paternal grandparents? Your own child, who is not your husband's, probably has another set of grandparents. So she has something that your husband's two children do not. Can you cultivate that relationship? Even by Skype or something if they are not here in the US - so you can feel that she isn't missing out on the grandparent thing? And what of your parents? Are they around? Would you really expect them to treat your husbands biological children the way they treat yours?
SO, I think in part you need to adjust your expectations to reality, have an honest and non confrontational talk with your husband and come to some better understanding of what to expect from your MIL.
And then, provided she's not "toxic", I think in this instance you should roll with the punches here. TO me, the examples you give do not sound like anything to get miffed over. Many grandmothers like to do things their own way (which may be what you mean by under play you) - this is likely nothing personal to insult you. Introducing your daughter to a neighbor with out you? What's the big deal? Maybe it just happened that she saw the neighbor - i would interpret this as a positive sign that she was "proud" enough of your daughter to introduce her.
Your other issue, which may be the bigger issue (s) - is your feeling of isolation and that you can't trust your husband? I am assuming there's a bigger reason you can't trust your husband - it can't be just over this. If it's over this, you REALLY need to talk this through because this is nothing to not trust him over. If there's another reason for not trusting him you need to get past that as well. Bottom line - there's not much hope for a marriage, especially a challenging situation with blended families, to last if the couple doesn't trust each other. marriage is hard.
Perhaps you can find ways to meet other local moms and even other people from you homeland to develop a network of friends so you don't feel alone.
OK I am babbling ut there's so much ambiguity and several things going on in your post I am trying to cover all bases.
Good luck!