Lots of disingenuous-sounding comments from several PPs about your barefaced CHEEK in suggesting that "a bride look" should be avoided at 70 ...!! Well, I know what you mean (I think)!!! I'm assuming you mean a traditional long white silk/satin/lace dress, fitted, & full-skirted or columnar - & I would fully concur with you, for two main reasons.
- OP's mum is on her second marriage. Loads of women post on MN all the time, who are about to be married for a second (third, whatever) time, asking for good alternatives to anything traditional - whatever the age they're remarrying at. The OP's mum has already done the traditional white bridal dress thing 50 years ago (even if it was low-budget).
- Even more relevantly, almost ALL women's bodies* *change with age - especially post-menopause. Usually, we gain weight, skin becomes less toned, our fattier parts (boobs & bum & stomach) feel the pull of gravity, & our bodies thicken - especially around the waist. We develop dodgy knees/fallen insteps/bunions/varicose veins & other age-related things due to wear & tear on our bodies. We might suffer badly from bloating, or have to wee a lot more often ... I'm simply being factual. And so - for MOST of us - how we dress does change with age (even without considering our changing tastes across the years).
So yes, as those earlier posters said, the OP's mum should be able to wear whatever she bloody wants on her wedding day at 70 - be it a strapless, boned, full-on meringue dress with stiletto court shoes & veil, or a silver sequinned jumpsuit with 6" platform heels.
But really - why would she want to ...? Surely the benefits of the grace & wisdom (hopefully) acquired with age allow us to choose what we feel most like ourselves in ...?? And for those of us over 50/60, we generally do not want to dress like we did when we were 20 or 30, or even 40? We will probably have a recognisable style that we've retained - but it has evolved, I would like to think. Perhaps even improved ...?!!
And from the messages that the OP posted above that she has exchanged with her mum about this thread, the bride-to-be certainly doesn't want to wear a tight white bridal gown - & has a sense of humour about the fact that she's "short & round & unstructured" ...!!
I'm twelve years younger than the OP's mum & will be getting married (for the first time!) sometime soon. At 58 the last thing I would choose to do is squidge my stomach & boobs in with some sort of corsetted undergarment, wear a tight sheath dress that displays my lack of waistline (I'm now more tube- than hourglass-shaped!), or teeter around on unsupportive heels that will wreck my weak ankles. But I WILL be wearing something bloody fabulous!!!
So there's no reason why the OP's mum shouldn't wear something in which she feels & looks fabulous too - but I'd suggest that a fitted white lace bridal gown probably isn't it ... 😁!!!