It is concerning that she would take without asking, but I think everyone else is right. Mainly I think that she just admires the things you (and grandma etc) have and she admires you as a woman and she likes your things. Its very normal. I would say she's really just taking without asking, I don't know if a 7 year old really knows what "stealing" is for sure. I'm sure she knows what to say so that she doesn't get in trouble, or so that she can keep the pretty thing she took without asking. That is to be corrected, but I don't think she has any vindictive motives behind doing it completely. Maybe she thought her friends would think it was as pretty as she thought it was, you know? And she wanted to show off. So what I think it comes down to is that she likes you and she likes your things.
I would say to have a long talk with her about why taking things without asking is wrong, and how it hurts other people, and how it makes her look as a person. Tell her that with certain things, if she would only ask, that you would let her play with them around you or you would allow her to borrow certain things. That asking and being honest would get her farther and in a more positive way than taking. Tell her it makes you sad when your things are gone and you don't know where they are. And its not nice to make people feel like that. Imagine whatever her favorite thing is, and ask her how she might feel if you took it when she wasn't looking and brought it to work and told everyone there that it was yours? And tell her what kind of people steal things from others, and that they look very bad for being so hurtful. The main thing here I think would be not neccessarily punishment but to help her learn some compassion and empathy. So she thinks about how she makes people feel before doing things, not neccessarily what kind of trouble she'll get in.
But don't get me wrong, if it gets out of hand, stealing definitely deserves punishment. I think its pretty normal though, I'm pretty sure I liked to have my mom's nice things when I was little too.
I hope things get better for you.