New doggy roommate: Nadi is being cool with her but they are not friends

So a friend of mine needed to go to Malaysia for something, I don't know what it is. It was probably just a vacation disguised as official business but I need to just tell her that she doesn't need to lie to me, just go on vacation if you want to. Why she would choose Malaysia for a vacation is kind of a mystery to me though.

Anyway, I am looking after her 4 year old Shih-Tzu while she is away and of course, Nadi is less-than-pleased about this.

Her name is Charlie and she is a sweetheart with a few rather minor issues that I find annoying and well, Nadi finds the dog's mere existence as annoying. She has a penchant for socks, especially dirty ones and will dig them up from around the house and bring them to her little bed that I have here for her in order to chew on them. A disgusting habit for sure especially since my socks tend to be very very dirty.

The owner of this dog lives in the same building as I do just one floor down but I can't with a good conscious leave a dog alone for all day every day, so Charlie comes up here with us unless I am leaving the house, which during the week on days that are not bowling days, isn't very often. I work at home and don't really have a lot of hobbies other than bowling so there isn't much reason for me to leave.

At night, things can get a bit uncomfortable because both of them want to lie right next to me.

Thankfully, Charlie kind of understands that the doggy bed area that is on my bed is for Nadi, and she is not to attempt to contest for it. Nadi doesn't get violent very often but she will lash out if something like a treat of a piece of "land" such as her treasured bed is at stake. The rest of the day when they are around one another they do not play but this is because Nadi doesn't want to. I am sure that Charlie would love to play but Nadi is 11 years old and Charlie is only 4 plus Nadi barely even wants to play with me and even then it is only during specific intervals.

Nadi is also quite protective of her "daytime corner" where she keeps her toys and goes to eat her treats. Here is a treat that she doesn't particularly care for that I bought a lot of but Charlie being here is helping out with the consumption of them. She doesn't really want the treat but she will not put it down because if she does, Charlie will approach and look like she is going to take it. It is funny to me that dogs are so protective of things that they do not even want, but desperately do NOT want the other dog to have it either. If Charlie wasn't visiting, I would end up finding that little treat discarded in the corner later on in the day. But because of our houseguest, Nadi eats them every time now.

The only complicated thing about having Charlie here is that I am the kind of person that takes dogs on walks several times a day and Charlie has been very poorly trained on the leash. She is constantly choking herself running in every which direction and on the few times I have tried to walk them both at the same time, the leashes just get seriously tangled up and i spend the entire time just untangling them. Therefore I have to go on twice as many walks since I cannot walk them both at the same time. This wouldn't be such a big deal if I lived in suburban America, but here in Vietnam the streets are jam packed with cars and motorbikes and are a very dangerous place for dogs to be even temporarily out of sorts in the middle of the street. I have had to use myself as a dog-shield on multiple occasions.

Even moreso than usual, Nadi is very nervous any time I stand up as if to say "you aren't gonna leave me here alone with that creature, are you?"

I do not. I have the keys to the apartment that is Charlie's home and anytime I have to leave the house, she goes to have some alone time down there while I am out.