When I installed the Sims 3 Setter to the game, I found out that when my games crashes during Create-a-Sim, so much memory was overloading the game, especially when there's more than one sim.

Does anyone know any way to prevent it from getting too much memory?

A few different things can contribute to CAS overhead.

• Too much CC, particularly if that CC itself is unoptimised (ie. higher poly or larger texture sizes than appropriate for the game engine).
• Deleting the CASThumbnails cache. This forces the game to regenerate the thumbnails, which is a memory intensive process.
• Clicking on too many different clothing or hair options in a single session. A few games struggle with loading too many assets within a single instance of the character creator, as this memory often doesn't get released until you exit the instance.

In general, it's recommended to separate extensive CAS usage from general play. This means rebooting if you've already been playing for some time and memory usage is running high already, saving before making new families or giving makeovers, and rebooting the game again once you're done.

If you're experiencing crashes even in New Game CAS or very brief sessions, I'd suggest removing all mods and CC and checking for that behaviour again.
Even with all expansions and stuff packs, it's not normal for CAS to be game-breaking.

I've been finding that a large number of hair retextures are an internal mess. Some reuse the original package, and add their uncompressed textures, without bothing to remove originals, which double bloats the package, and puts a memory strain on the game. I've even found solid black speculars as 1024 x 1024 uncompressed, which is just silly.

To fix this one issue, you need to know how to use S3PE and an imaging program. Texture Tweaker may wwork, bbut I have never used it. I open the package in s3pe. Very often, a hair package that is more than 6,000 kb will have issues. Select an image. S3PE often shows text in the preview window of uncompressed images. I will export all images to a work folder. An uncompressed 1024 x 1024 image will be over 5,600 kb, whereas dxt5 is around 1,300 kb. Import the texture to GIMP or whatever, then export as dxt5 with mipmaps. Use a new name and hold the original incase the hair actually does look bad in game... but highly unlikely. Replace the uncompressed images with your compressed images and save. Test in game.

Bloated hair is my greatest foe, since I am a hair ho!!! Is more than 5 GB too much???

Also bloated with very high number of polygons - I'm sure that a 30k hairstyle to be 15k or oven 10k polygons and still look good and not put so much pressure on the game.

Maybe. But once made at a high poly, tools I know of don't often maintain appearance while reducing the count. And sadly, I admit to being guilty of high poly regarding quite a few of my MMD or XPS to TS3 conversions, especially my FemmeBots, and a few other recent MMD/ XPS conversions. I've even gone as far as foregoing morphs because I find it impossible to reduce count enough, and maintain mesh quality/ appearance.