Tea Kettle snickers, and I point indignantly. [as an aside, in British English no need for the "Tea" in connection with a kitchen, since a kettle boils hot water which can then be used for anything, including making tea. Not sure what is different in US English between a tea kettle and anything else which boils water]
"It's not alive." [I assumed this was "I" speaking, ie asserting the kettle isn't live, but now I've read your explanation I think it must be Mother. This needs to be clearer, I think]
Mother never sees, never hears...
"What about the ketchup indecent?" [I don't know who is saying this -- and as a result none of the rest of the dialogue can be attributed as I go through. So to me you need something like "I said/continued" or "she continued/retorted" as appropriate The punctuation is fine but the last word should be incident]
"Sleep walking prank." [Sleepwalking as one word --which would have helped allow for the dialogue attributions needed]
Toast cackles as she is buttered, they think it's fun to tease me. [this is a comma splice -- where the comma acts to link two clauses but isn't enough to do the job. I'd suggest a semi-colon or a full stop (period)]
"and the quiche?" [capital "A" for the "And"]
"all I know is; the kitchen is just a kitchen, food is food, and if you keep this up we'll have to send you to a home!" [This line I understood as coming from Mother, so I then had to go back and work out the others from it. You don't want to have to rely on it, though. As for punctuation another capital "A" for "All", a colon instead of a semi-colon, and unless she is joking, delete the exclamation mark (point) as it makes it sound as if she is not serious. And again this may be a British/US English thing, but I wouldn't use "home" here, as to me that's for old or ill people (ie nursing or convalescent home) but rather "institution" or "hospital" or if Mother is being offensive "nut house" or "loony bin". The latter help to give an element of characterisation about her, too -- not just that she's insensitive, but also deliberately unpleasant/aggressive]
She walks out munching Toast, who is still cackling.[good last line now I understand what is going on. I understood it was Mother as you've used "She" so that's about the only line you don't need to worry about!]