I like the style of the alma, but prefer it most in Vernis. Have you considered the Vernis Alma? I don't think the style is too mature for your age at all, I just think the vernis is a lot of fun! Between the Damier Alma and the Tivoli GM I would vote for the Tivoli, but again, only becuase I like the Alma in vernis. The Tivoli is a gorgeous bag, also totally age appropriate. You can't go wrong with either bag! Good luck with your decision!
The Tivoli is a classic and you don't see many of them around. Hopefully either the PM or GM will be my next bag.
I don't like the Alma shape, I was looking at a Damier Alma (when I ended up purchasing my Ribera) and the one the SA showed me had a "deep" scratch along the base, underneath. Ok it was the display piece but it looked so ugly and I could easily see how this could happen. Put me off Almas for life!
I only like the Tivoli in PM size; GM is a tad too bulky. So between the two my votes goes to Damier Alma - it's a very classy and feminine bag! But yes, I do agree that the vernis alma PM is the best! It's the best line for alma IMO.