Coco and Poppy have started fighting

Coco my staffie and Poppy my lurcher have started fighting. They are not little fights either. They started off ok together. Coco always starts it but once started Poppy will not give in. The most recent fight being today. I don't know what to do. It has got to the stage where I'm thinking of rehoming Coco, but she is going to be really hard to rehome as she has a skin condition and lots of fur loss. She gets on great with my other 4 dogs and lies with Poppy most of the time but when they get excited she attacks her. Poppy does nothing to provoke it. I'm totally devastated at the thought of having to rehome her. She needs us. But I fear for Poppy.
Does anyone have any ideas that may help?
Both Coco and Poppy are unneutered at present but we were going to get Coco done in January. The research I have done suggests that neutering rarely helps in females.
I don't want to rehome Coco but at present I cannot see any other option.
PS I have another female, Jenny, and she gets on great with her.

"If a bitch displays dominant aggressive behaviour then she should not be spayed as this will exacerbate the problem due to the lowering of oestrogen levels. " i've seen a few quotes like that but no idea if it's true also i remember something about spaying the less dominant one and leaving the other intact? What age are they?.

I think you need to watch them carefully and step in strongly if you feel that Coco & Poppy are getting too lively, before any fights start. If you get into the habit of stopping them before they start (if you see what I mean) it will help enormously & will reduce problems.

I'd also seperate them when they are unsupervised, just in case.

How old are they both?

Agree with Caryll. You could also try only have them around each other for short periods of time and increase the time together if they are getting along.

Thanks for your replies. They're both rescues so we're not too sure of their exact age but we think they are around 2/3 years of age.
Since I wrote the original post, Poppy has been to the vets as a result of this last fight. She had to have stitches and drains put in. She's a lot more comfortable now and we are keeping them separate which isn't too much of a problem at the moment as Poppy is very tired and full of painkillers so spends a lot of time in the room with us in a crate asleep whilst Coco is out in the room with us.
We do keep them separated when we're not there anyway. But this happens when we are there.
I cannot bear the thought of losing Coco. She is a sweetheart in every other way.
Until we can figure out a solution and get them spayed, we're doing "swapsies" between the two of them.
Graham is going to take Coco to the shop every day so Poppy can have free reign in the house whilst she's out.
They started off so well together. I'm gutted.
The only hope is that, when we first got Jenny, she hated my collie, Bessie but she has settled down enormously since she was spayed and has turned into a placid, lovely girl. I'm hoping the same will be true of Coco and Poppy.
The trouble is, Coco is trying to be dominant but Poppy is no push over.
Any more advice is really welcome. I go on another forum too and the only advice is get rid of Coco!! But she is vitually un-rehomable due to her bad skin and fur loss. Then someone suggested I have her PTS! How can I do that to my otherwise perfect baby? I just can't.
It is such a refreshing change not to have people just say "PUT TO SLEEP" and I thank you for that xxx

I don't think anyone here would ever advise PTS for behavorial issues. Swapping the dogs out is a good idea. If Coco is getting on fine with your other dogs the situation should be managable. If they are around each other maybe you could keep them both on lead and watch the body language very carefully. They could learn to get along in time.

I really do hope so. When I look at Coco I just want to cry. She adores us and is so happy here. And Poppy just looks so pathetic.
Dogs......I love them dearly and they're so much fun but can cause so much heartache too