To a large extent, Lenny's expectation of Meg when she comes back home is a sense of acknowledgement. Meg had always retained the lion's share of attention from others and had been the "main attraction." It is for this reason that she had left and pursued a career in show business, in the first place. With her arrival, I think that Lenny had wanted Meg to display some type of understanding at the unfairness, or perceived unfairness, at how Meg received more attention and more favor from others:
Why should Old Grandmama let her sew twelve golden jingle bells on her petticoats and us only three?
Lenny does not immediately receive this level of validation, as Meg reverts back to the role with which there was immediate familiarity. It is for this reason that old jealousies resurface in the course of the sisters' interaction. Yet, it is for this reason, also, that there is a sense of understanding and eventual acceptance between the sisters. I think that the initial expectation or hope that Lennie has is that Meg's return brings with it an understanding of this emotional dynamic, and the necessary tools to rectify it. I believe that it is to this end that the emotional timbre between the sisters is one of both anger and resolution is established by both Lenny's want of her sister and their eventual acceptance of one another.