Vacation Photos in Shared Album

We recently took a vacation with my sister's family. I created a shared album with our photos, and she has added her photos to the shared album. I don't fully understand the mechanics of shared albums, but I believe her photos are not actually in my Photos library. I would like to be sure to have them there for the long-term. I've tried just selecting every photo in the album and dragging them to the photos tab in the sidebar, but my Photos app just crashes.

Is there any way to sort out the photos she has added from my own? Any other easy way to get these photos into my Photos library? I'd basically just like to treat these like my own photos.

I'm on a 2017 iMac with all software up to date. I do use iCloud Photo Library, though I don't think that plays into this issue. There are almost 800 photos in the shared album, about 500 of them are mine. We both have pictures taken on iPhones, mine from an iPhone 8 and hers from a 6S. I think that may be one way to sort them, but I'm not sure about the right approach. Thanks so much for any help!