My response copied here -

Very very tricky. You cannot allow aluminum wire to touch copper wire. Galvanic corrosion, different expansion rates, literally playing with fire.

You need special connectors called AlumiConn to pigtail safely aluminum to copper. Your link didn’t work, Here’s mine.

Now, all that said, there’s not one dang thing wrong with properly installed aluminum wiring, especially in an older home that has been operating properly for years.

Your biggest issue with pigtailing this is bending the aluminum wire. It doesn’t like that and will crack on you if it’s bent too much or too often. So watch out for that. Be very gentle with it.

On the existing stuff throughout the home, removing them only flex’s the aluminum wire again. I might just remove the plates and inspect with a flashlight. There are special plugs and switches for aluminum and/or copper wire available and hopefully anybody before knew that and used them. I think you an tell by looking. Both screws may be silver on the special devices. I’ll let you figure that out. If you use them, you won’t need to pigtail.

Good luck and be careful. Make sure she has good smoke detectors.