A bitch I co own regularly pulls out her  coat when with the co owner.  She doesn't do it when staying with me.  From what I understand there is no change of food etc but the resident bitch who lives with the co owner may be in whelp.  I am wondering if this could be the cause of this coat stripping.

Any ideas?

I'm not sure how true this is, but somebody told me that dogs sometimes strip their coats when bored or stressed   maybe she's happier when she's with you!

Is she kept in kennels or an indoor dog?

She is an indoor dog.  The only difference I can see is that she probably gets more field exercises with me.  At home with the other owner she plays in the garden with the other dog, also a lively breed and has weekend runs out.  It is really hard to pin this down and I don't want to be heavy handed about it but I just feel it could be sorted.

Many thanks for your input Sharon.