Hello, yesterday I was trying to solve this same problem and this is what worked for me:
I had tried EVERYTHING suggested by every possible post I could find. All the cheats for aging and even the ones for resetting. I had tried the cake many many times and editing the town, moving my family out using the phone or the town editor. Evicting the family and even edit the sim itself (a toddler who was also a girl werewolf). Some solutions did nothing, some others made my game freeze.
Finally, I did the resetting of the game as it IS mentioned above, but that gave me much more problems than what it solved, so I put the files back (even the custom content). My main problem for this was, perhaps, that my game was in Drago Valley (and this is an extension that is connected to the CC). So, while I was copying my content back I noticed 2 folders for my saved games (saves folder). The first one had the Bridgeport.sims3 (I think this depends on the kind of city you save your game) and the other was bridgeport.sims3. backup. I checked those folders before copying them back and I noticed they had very similar files with different last saving dates. They seem to be in pairs staring with the name of the city you've ever played. So you have a couple of files starting with the name Frace, for instance, if your Sims have ever been to France and I noticed there were a couple of files starting with the name Dragon Valley but with a previous date as the last modification. I immediately assumed this was my previously saved game and I thought accessing the game through this previously saved position, would give me a chance to prevent what had gone wrong. So I replaced the 2 files in the bridgeport.sims3 folder and I opened the game.
I was quite happy to discover that, by doing this, I not only was back in a previus saving point as I had thought, but I also was able to see my toddler in the pictures again and I could see her face when selecting her to do an action. I was able, even, to edit her using the mirror (all these actions were troublesome before). So I played for a while and I bought her a cake and I had the same problem again. I signed out without saving and I tried many things so, this is what really worked:
*I removed the custom content in my baby (it was just hair) using the mirror.
*I made sure she knew how to talk, walk and was potty trined (just in case)
*I used the cheat to age her instead
And voila! I have a lovely girl now! I edited her in the mirror just to see what hapenned if I gave her custom content (I used a different hair this time) and I discovered, her hair changed from custom to a regular kind of hair for no apparent reason. So I think there's something strange with her so from now on I won't use CC on her.
I hope this helps somebody with this same problem, since I think maybe you gave up or solved it in a different way (so share if you did, please!).