Someone who has a great taste in fashion could help others with their shopping, but as a profession not as a hobby.
The inspiration for this question is from the movie "In Her Shoes".
A 'personal shopper' (reference.com) does this, and may be employed by the shop or independent.
Personal Shopper/Buyer's Assistant
normally you can use many words but the one that best describes that is doradca. THe pronunciation however is not known to me. The word has been in use for last 300 years - so it is hihg time to learnt it and use freely