I guess we'll never know; what we find out is that Elly feels martyred.
Panel 1: Today's reprint starts with Lawrence, who's carrying that suitcase we saw yesterday, being greeted by Mike who says "Wow! You get to stay a whole week, Lawrence! You get to stay in my room and everything!!"
Panel 2: He continues to talk like a real six-year-old by yelling "Lawrence is staying!! Isn't that fantastic, Mom?" to Eyeless Elly and Barnacle Liz.
Panel 3: As Lawrence and Mike's silhouettes jump up and down and Barnacle Lizzie screams because of the noise, Elly says "Just wonderful" in a wounded, despairing tone of voice.
Summary: While I do know that this isn't going to be an easy week for her with two active, healthy boys whose need for stimulation will confuse, horrify and overwhelm her under foot, it seems sort of odd for her to get all mopey because she volunteered.