Ah, right... okay, let me correct you then because you clearly played it. The woman (Jenny) doesn't vanish, she goes on a jog (I added that line five times when Jenny says I'll go jogging now). The sneaking part is intentionally made wrong, you were learned by a scammer! The game never meant for you to leave the house. The content of the game is pushed mostly by side conversations (you're not forced to do them)... and finally, it's not a walkthrough they are tips (showing hints to help you clear the next objective if you skip conversations).
To answer your question about Mia.
Whatever you choose to show/not show, she will have a different conversation... this can be seen when you talk to her in her room or the kitchen. This option does not limit what scenes will you have, but some major events further into the story. You can't make her mad, she loves MC and this relationship is pushed even further in the last update.
Seeing you still here means you like the game so far. Enjoy.