I agree with the first precedent you give. I had overlooked that - thanks for pointing it out.

I'm not so sure about Fanny thinking it would be presumtuous for her to envy Mrs Rushworth. I've always taken it to mean that it simply hasn't occurred to Fanny to envy Maria, or that if she thought about it at all she wouldn't be interested in either Mr Rushworth or his wealth. You could be right though, so I'd say the point is ambiguous.

Mary certainly seems to have reverted to her London mindset very thoroughly. Looking back to the time from when Edmund goes away to be ordained to when Mary and Henry depart for London together, (a period of about three weeks according to Ellen Moody's chronology), we see glimpses of a softer, less mercenary Mary and she shows she has gentler, more reflective possibilities:-

Ch.29 - Mary is missing Edward and feeling jealous of the Miss Owens.
Ch.34 - Mary welcomes Edmund warmly when he returns.
Ch.36 - Mary's reverie in the east room.

From Fanny's perspective (ch37) ... the doubts and hesitations of (Mary's) ambition were .... got over ..... without apparent reason.

I wonder if part of the reason for Mary's seeming change of heart is the indirect influence of Henry. First he paints an agreeable picture of how Thornton Lacey could be with a little 'improvement'. More importantly, his enthusiasm for Mansfield and for marrying Fanny Price (the poor relation) might suggest to Mary that he would regard a marriage between her and Edmund with approval. By marrying into the same family would also keep her in close contact with her brother.