I am starting to have awful trouble with my 6 months old puppy. She is a rescue who I have had since 9 weeks old and she has started to become very aggressive towards my other dogs. She will lift her lip at them if they sniff her or walk to close and she will lunge if they get up on the chair or bed beside her. I feel like at my wits end now and have gotten to the stage where I just don't love her anymore. She used to get on fine with them but was always a little bit nervous as Simba my older sheltie would give out to her sometimes. I've never had an issue like this with a puppy and would appreciate any thoughts or advice. Thank you!