Ooh i would tread carefully on the gift to display as people have unique taste levels. Apart from obviously supporting my friend i would instead give something more relevant what she may perhaps use instead. So my idea is to give out something fun along the lines of a stress buster kit, a nice hipster mug, emergency tea bag, personalized note book to plan nights out with you! As you know your friend well, so put things that you know will de-stress her as running a salon is stressful!
One of my oldest friends brought me a peppermint cooling gel for the feet- it was perfect as she knows im constantly on the go with my feet and i wear tights all day long, it's a bit of an in joke as i get swollen feet and well they really smell--(pong in fact)- it was her idea of poking fun at me, and well i love it! My sister brought me a lunch box and oh its so cute, she had left me a post it message in the lunch box with a sweet message, i actually keep it in my kitchen and it makes me smile everyday!
Just a few ideas to get you thinking! Have fun shopping! xoxo