Yes, she lives alone -- although in theory Kody should be spending 1/4th of his time there (I doubt he actually spends 1/10th of his time there).
I know this has been discussed in different SW-related threads, but I can't remember if there ever was a definitive answer as to how the money gets split between the wives. It seems to me....although I welcome correction if I'm wrong....that generally money is split evenly between the wives or, at the very least, the number of children any wife has doesn't seem to factor much into the calculations. So, Janelle, Christine and Robyn have had to cover food, clothes, wedding expenses (in the case of Janelle and Christine), living expenses, etc. for multiple children, while Meri has been an empty nester for years. Why she feels that she "needs" a huge rental house is mind-boggling. We've heard discussions ad nauseam on the show about how the quick sales of the homes in Vegas and the resulting incoming funds are critical, yet Meri doesn't seem to be willing to "take one for the team" and just live in an apartment. (Just did a quick Google search and, per apartments.com, there are currently 374 apartments for rent in Flagstaff.) If she's unwilling to make such a sacrifice, you would think that she might want to spend less on rent so that she could stash away some of the money that she's currently spending -- that way she'd have a nest egg if she ever decides to leave.