Keratin Treatment

I think this has been discussed before, but I can’t find it...talk to me about keratin treatments and IBE. I have an extension client who is actually the color client of one of my co-workers. The client wants her to do a keratin treatment on her in a few weeks. My co-worker is just planning to apply it only to her natural hair and work around the extension hair. Or should we just take the extensions out, have her do the treatment and then re-install? Thanks!!