
Hi Lucy,
Is Ellie speyed - if not this could be hormonal, a season coming on ? If she has been done, can you think back to anything specific recently that would have made her more over-reactive than normal? Sometimes we miss obvious things when we are too close to a situation.
Unfortunately if one dog is on edge it will most probably affect your other dog too :( If only they were all as quick to learn off each other the good traits :rolleyes: Try if you can having them separate for a while at home and on trips out. This will give you a better idea on what each of them is most likely to react inappropriately to. It may well be this will give you an obvious pointer with Ellie and also show that your BC is fine when he doesn't have her around to set him off.
Not that any of the above will immediately solve your problem, but may just help you to define exactly what the problem(s) you're dealing with are.
Hopefully someone else will be along soon with useful info.
Regards & Good Luck,
Teri :)