I was never tempted to be so hard on her, for the reasons you note. She's doing what she thinks is best for Anne. You might add to the list that Lady Russell had "prejudices on the side of ancestry: she had a value for rank and consequence,. . . . Herself the widow of only a knight, she gave the dignity of a baronet all its due . . ." (chapter 2). Frederick would have been a poor match for these reasons as well.

I feel like I'm BSing with the following--I haven't studied Austen well enough to be sure this analysis is viable--but perhaps Lady Russell is occupying a sort of middle ground. Sir Walter obviously cares for nothing more than his title and his station in life, and so he will scrutinize any marriage prospects for his daughters in such terms. In chapter 1, Austen implies that Sir Walter's view is that "Mary had acquired a little artificial importance, by becoming Mrs Charles Musgrove". I could swear there's more like this implying that Sir Walter doesn't think much of Musgrove, but I can't find it at the moment, or perhaps it comes later. As far as his rank in society goes, Charles Musgrove is just barely good enough for Sir Walter's daughter.

Anne on the other hand sees that love and mutual regard are what matters most in a potential marriage partner.