She may have been hurting or feeling bad or just scared to go outside due to some scent or bark or noise she heard outside and it put her off going out voluntarily but when you leashed her, she realized she was under your control and just went out rather than be pulled along. Or, by the time you leashed her, whatever she was worried about was no longer worrying her. Or, she's got such positive association with her walks on leash that it made her want to go out maybe thinking she was going for a fun walk. But likely something out there made her a little anxious about going out voluntarily and hopefully it's all gone tomorrow.
If she keeps it up, I'd have her checked over by the vet and if he gives her a clean bill of health, try distracting her with food treats and leading her out with those in front of her nose until she voluntarily goes out on her own.
__________________  Jeanie and Tibbe One must do the best one can. You may get some marks for a very imperfect answer: you will certainly get none for leaving the question alone. C. S. Lewis |