Dog urinating inside on purpose

[RaveclawZia13]

My 2 year old Shih Tzu has been extremely hard to toilet train. We have weeks without an accident and then suddenly she will wee in the house again.

The past week though we have had my in laws visiting twice with their springer spaniel who is 8 months. He can be a bit much at times for her but sometimes she likes playing and dominating him. He is kept on a lead although it's a small house so he can't get everywhere and she can have her space. She has purposely peed inside the house both times they came. Today she peed outside and then came in and squeezed a bit out inside.

We are fairly sure she is punishing us for bringing a dog that sometimes annoys her into the house but don't know how to prevent it. We never scold her and never will but we are unsure how to proceed.

Any advice?

She's not punishing you - dogs don't think like that ...

... she is marking her territory, ...

She's a dog, not a manipulative human!

I would think she is marking because of the other dog.

Okay okay maybe my wording was wrong. I knew she was doing it deliberately I'm just unsure of how to prevent it as she has not done it before with other dogs nor has she done it when this specific dog has been in the house before.

I know we need to keep a close eye on her but is there anyway of helping her past it.

I would imagine she feels her space threatened by an invading adolescent male and she's marking her territory to communicate to him that the space is already taken. She's feeling stressed, not angry or vengeful.