My sense of smell is non existent but I can buy perfume
Tips one: Find out the brands she covets. For me, as a middle aged middle class couple, it’s not so much mainstream Debenhams, think likes of White Company, Space NK, Jo Malone, blah blah i.e. Semi posh high street fur coat no knickers aspirational. At the end of the day, it’s as much about the brand and packaging as it is about the scent.
Tips two: go to the most expensive shop in your chosen field
Three: Tell the sales assistant you are an idiot. Ask them what they like best and what is selling well. It helps if you know what kind of thing she likes, when she will wear it, etc. Chat about it and take your time. Try some if you like but for me it’s next to pointless.
Four: pick one and buy the most expensive format you can afford. Remember, a little goes a long way.
Same method works for lingerie, but you need to be brazen about it.