I can't say for sure because I've never had this error, but it's possible that either you or the person who made the model are using an older version of the program.
In versions before 1.2, you also needed the image files in the exact same place as the originals for the program to load it properly. If that's the case, then try this:
First, confirm if both you and that person have the latest version of the program installed (1.3).
If she was the one with the old version, then ask if she can update the program, re-save the model in the new version, then send you the updated file.
If you're the one with the old version, then update and see if the model works in the new version.
If you both had the latest version, then I have no idea. You can try asking if you can have all the files involved with your model (so the folder with the sprites + the .save file), save it exactly where she did in the Pngtuber Plus folder, and seeing if the program can load it then. But, supposedly that shouldn't be necessary in version 1.2 and onwards, so I don't think it'll help if both of you have the latest version.