I really don't think calling Cobel was as ridiculous as people think

My first reaction when Devon called Cobel was the same as a lot of you, "wait, why the hell would you call HER!"

But, I've thought about it a bit and it does actually make sense from Devon's perspective.

We've seen how fanatically devoted to Lumon Cobel is, but Devon has never seen that side of her, neither has outie Mark.

Devon has only ever seen her as Mrs Selvig, the nice and friendly persona she was putting on. Obviously, Devon now knows that it was a ruse, but she doesn't know to what extent exactly she was faking her personality.

More importantly, there is one thing Devon knows about Cobel with 100% certainty; she knows Lumon just stabbed her in the back.

Just that fact alone is enough to think that maybe Cobel would be willing to work with them. If you knew that somebody had not only been fired from a company, but also had that company pin the blame on her for a huge mess, then it's not unreasonable to assume that she'd have a grudge.

It seems like a bad idea from our perspective because of how fanatical we've seen Cobel behave. But you wouldn't have that impression of her if you cut out 90% of her scenes and just watched the ones with her and Devon.

EDIT: I mentioned this in the comments, but I think it's worth stating here.

It's not just a question of "should I trust Cobel or not?" Mark just had a seizure from surgery performed on him in his basement and the situation seems pretty dire, so she only has two options; trust Cobel, or trust the sketchy lady who just performed that surgery.