Hilariousness of the pic aside, I can't figure out what the first line is. "The bed's so {musu}"? Unless that's not a mu... Not sure about the "げきまおー" near the bottom either.

According to edict:

蒸す: むす (v5s,vt) to steam; to poultice; to be sultry;

Does that make any sense?

How about mazu(i), kids?

I still don't understand that first phrase: ねどこムスのよね〜

I don't see any better options than 蒸す. "It's so hot in the bed...", and then she goes right for the cup for some refreshment.
げきまず is げき+まずい