Astrid, my mum is in a similar place to you at the moment (she is 49. however she isnt the typ to wear the 'older' style clothes, IYKWIM)
i know she shops at Millers (you have to get the right store, because apparently each millers has a different range!) also, Target has a lot of nice stuff!

i have always said to mum 'dont ever think you're too old to browse in certain shops...' ok, something like JayJays probably wont be of any help.. and supre. but shops like Cotton On.. i LOVE Cotton On. they have a great range of 'basics' and always have sales '2 for $xx' Just Jeans? Portmans? Glassons... it never hurst to just have a look, and see what they have.

i hate clothing sizes with a passion... i was actually thinking of making a post about it yesterday! i rarely look at the size tag, i just look at the item, and think if i would need bigger or smaller. i do the same for DD.