Photos syncing with daughters iphone

Hi

My daughter and I have always shared apple ID's (approximately 3 years) and we have always managed to keep our own photos on our phones but also been able to upload our pictures to iCloud. Since Friday however, photos appeared on each others phones.

I checked the settings and I had photo sharing turned on (which is strange because this has always been turned off) so I turned this off and my daughters photos were removed, however this also turned off the iCloud photo library toggle (again which I thought was strange). My daughter also did this but this removed 90% of her photos, including all of mine.

To cut a long story short, now we cant stop photos from sharing without either of us having any of our original photos kept on our phones. When we both turn off iCloud photo library we only have 450 picture which are a mixture of both mine and my daughters (I had 4500 photos on my phone and my daughter had 1500).

Can someone help and suggest what we can do moving forward without my daughter having to set up a brand new apple ID.

Thanks