Hi all i'm new to this forum and i really need some help. I have a 12month old staff/ border collie cross who has recently started being really aggressive towards me. I have had her since she was 8 weeks old and besides some teething problems (nipping me while playing and when i put the lead on her) she's been great. for the past couple of weeks shes started being really aggressive towards me biting me when i have hold of her collar and when she's tired which im finding really upsetting. She use to be such a loving dog and i really want the old milly back. The only change I can think of recently has been that ive started taking her out with my friends dos (also a staff cross) who she plays with in quite a rough manner. She's had one season and and is due to be spayed on wednesday. Please please help i'll be so greatful for any advice.