My 13 week collie was very good with walking on a lead but these last couple of days she has started to jump up and bite her lead. At first it was 1/2 way through a walk and would last only a couple of minutes but then it happened as soon as we left the house. At first I would wait untill she finished! but she would end up biting me as well. Then I tried holding her off but was frightened of strangling her! Today she did it minutes after leaving the house so I turned round and came straight home. After a few minutes we tried again but the same thing happened so I turned round and came home. Will she realise that if she bites her lead she will not get her walk?? We let her off on fields/beach so I think thats why she bites to be free. Whats the best way to handle it.