Have your mom do it, then.

Tell her no it's your life

I'm assuming since you're old enough for jury duty you are an adult. Why exactly did your mom do this without asking you? Perhaps just don't do it.

You do need to talk with your mom and inform her that she should not volunteer your services without asking you. You need to tell the friend that your mom did not ask before volunteering your services, and you have obligations you cannot drop. Maybe also block the friend of your mom.

There is no contract here because you are not receiving any consideration. She is solely benefitting from the execution, therefore this contract is "voidable". You are free to house sit for her, if you want to, but you are under no obligation to do so, nor does she have any recourse should you decline. Now, had you agreed to housesit for the sum of $10, and then decided to back out, she could sue you for failure to perform and you would be liable for any damages she incurred as a result. For example, if it cost her $100 to get somebody to house sit, you would be liable for that amount, because of your actions. Bottom line, your Mom made the promise, she can house sit.

So don't do it?

Damn, that lady needs to relax. It's just a home, it won't get sick or run away.

That sound too familiar!

That's BS. Just leave. You weren't the one who offered to do it; and if they lady has a problem with it then she can take it up with your mom.

If you're old enough for jury duty you're old enough to tell your mother no. You won't house sit.