Not getting the point

EM: do you understand how the sizing works?
Cust: yes... What does this size mean? (holds out the tag)
EM: so that is a size 14 across the shoulders and around the waist but a roomy size 14 on the bust
Cust: oh, that's how it works, and this one? (holds out another tag)
EM: that one is a size 18 across the shoulders and around the waist but a size 22 in the bust...
Cust: I don't really know what size I am
EM: it's all to do with what size you would take to get something fitting comfortably over your boobs and then what size you would take to get something to fit around your waist
Cust: I don't really know, I'm a size 10 or 12
EM: ok, so if you bought a size 10 shirt, would the buttons pull?
Cust: not really, I don't think I have that problem, is that what this is for?
EM: yes, it's so you can get something to fit everywhere and not need to go up many sizes to get anything done up
Cust: my problem is my hips
EM: right, so I would say try a 10 in the smallest size then
Cust: I've out on weight as I've just got back from holiday
EM: oh, ok
Cust: (pulls top up to show waistband of her jeans) I mean, these are a ten but there's room in these (looks like she should be a dress size smaller but there's no way she would get in an 8) so I don't know
EM: I see
Cust: (picks up a dress) this is lovely, but it looks like a thick dress, not very summery (it's a crochet dress) I doubt it's cotton (the crochet bit)
EM: let's have a look at the label and see (checks label inside dress) 100% cotton
Cust: but the lining isn't?
EM: no, because then the outside would ruche up and stick to it
Cust: oh, we'll I'll have a look around and see if there is anything I like
EM: ok, sure...