I don't know who these people think they are fooling. OK, maybe some cosmetic surgery is undetectable (in which case why bother?) but in many women, it's immediately obvious because of that stretched look around the mouth, more prominent cheekbones. and the slightly cat-eyed look they can end up with.
That's OK, it's their choice, but why lie, especially to old friends? You're not going to be taken in, and you know exactly how old she is. If women colour their hair, wear lipstick, use fake tan, they don't usually pretend they haven't. Your friend seems to be ashamed or embarrassed at what she's doing, but It's sad that she is putting her own vanity before the need for honesty with her friends.