get a rope or something maybe tape and lock it
if you are impatient set the house on fire.
or she could starve inside there or something not getting her bodily needs
the answer is. You can’t leave any chance for her survival because she knows what you look like. Here’s what you do. You call her phone and when she hears it ringing she’ll think it’s a chance to escape. You hide next to the closet and wait for her to come out. Once she leaves the closet you stab her. Stab her a bit more. Then slit her throat. At this point she’s already dead. Now you dispose of the body and remove any evidence you were ever in that house. Make sure to wear gloves during the mission too. Once it’s finished you leave the house as it was when you came except the woman isn’t in it. Everyone will think she’s gone missing and when they never find the body because you incinerated it it’ll be another unsolved mystery to the people but you know exactly what happened and know that it can’t be traced back to you. Not anymore at least… mission successful.
Dam I really am a psychopath.