I'd see it as cool. like saying, "you're mom is cool" Fashionable? yes indeed but i can't say it suits her as the same reason there are many types of clothing and one of the reason is age appropriate. However, again these were all made to be followed so there is nothing wrong to be different and some can carry themselves well. If he/she feels younger, prettier, more confident or whatever reason he/she has, as long as it is appropriate for special occasions, no problem for me.
When it comes to fashion and hair I say do whatever makes you feel comfortable and happy - It might not be to everybody's tastes but so what - I suppose my answer is somewhere between A and B, I wouldn't encourage it but I wouldn't criticise it either.
If they age well and still look relatively young, it's whatever. But if they age poorly and look older than their age, then nah. It looks weird. The grandma just looks ridiculous to me in your example photos.
im nearly 40 and still dress fashionably... why shouldn't i. i look fucking stupid in 80s clothes wouldn't i? i do see your point but given the pictures you have chosen i think you are mistaking fashion with ridiculous. i dont see any young people round here dressing like them and infact that colourful outfit you show is definitely 80s madona