Sounds like the house belongs to OP’s dad or grandpa. 

OP, only the owner or the tenant can kick out a guest, unless the cops catch her in the act doing something absolutely illegal, like selling drugs. So getting her out may take a while. 

In the meantime, you and your sister should definitely talk to your mom, dad, and grandpa about your concerns. And there are things you can do to protect yourselves, like making sure that all the smoke detectors function properly, and having a fire escape plan in place. Check out https://www.nfpa.org/Public-Education/By-topic/Safety-in-the-home/Escape-planning. 

And if your stove is a gas stove, the house will have a master gas switch for the stove, usually behind the stove or in the basement. You can shut off the gas to the stove with it. It looks like a knob or a switch attached to a brass pipe. Maybe your dad would agree to turning it off every night, without telling your aunt. You can turn it on again in the morning.

Edit: and maybe you could get a fire extinguisher for the kitchen. You can get them at Home Depot, they are about $30.