Hi, I am hoping that someone can help bring harmony back into my home. I have a 9 yr old JRT x Papillon a 2 yr old JRT and we have just re homed a 4 yr old JRT x Chihuahua. I work at a re homing center and we had the JRT X Chihuahua brought in to us as hand over as he had bitten his owner. He was very nervous aggressive and shut down and would bite everyone that went in to him and wouldn't let anyone handle. Because of this we couldn't put him up for re homing. I spent a lot of one-on-one time with him and he eventually started to open up and turned in to a friendly little dog with me. My boss agreed that I could take him home as long as I was responsible about who he meet and he was muzzled when out walking. He has now been with me for 3 weeks and has been a little star only a few nips but all in all a happy little dog, with me and my partner. The problem that we have is that my 9 yr old Jack x Papillon hates him. She will follow him around the house staring at him until he starts to grumble at her ( i think the only reason he does this is because he's scared and reacts ) but the the more she stares the more he grumbles she will then start trying to fight with him. They do not actually bit each other and he tries to get away from her but we do have to split them and it is very upsetting for everyone. I feel soon it will escalate in to much worse that just noise and the fight are now happening 2 to 3 times a night. We have tried to do so positive training with her when he is in the room but she just will not let it drop. She will not settle and will not get in her bed or relax when he is in the same room and will just fixate and follow him round until he reacts, then she will attack. I think it all steams from when I first brought him back and he was on the sofa and nipped me while I was trying to get a sock off him. She then went for him and they had their first fight. Can anyone please offer any advice it is getting to the point where one has to be in a crate while the other is out. I do not want to have to take him back and I don't want either dog to be unhappy. My 2 yr old JRT is very laid back and him and the new dog get along brilliantly but i think the fight between the other two is starting to unsettle him as well.