The issue of how to recover from a volume which became full has been discussed on this forum. If you ever need to do that it won’t help to delete any snapshots at all, since snapshots are only virtual representations of a state of your source at a given time.
So, you will have to turn your attention to any recently written blobs, which hold the actual data and you will have to manually delete some of those. Afterwards it will be a back and forth between snapshot verify and snapshot repair.
You may want to take a look at this thread: Disk full - Snapshot delete not possible !?