Yikes. So sorry that happened! It would have been easier to remove from the canvas so it's even more unfortunate that it's on the leather. I would try to remove it with a credit card or something, see if you can scrape it off.
A google search of "remove chewing gum from leather" came up with this:
Please listen to the ice solution. I work in a furniture shop that sells leather suites and the answer to your question is ice. When you freeze the chewing gum it becoms hard and it will peel off without without leaving a mark. The same principle will work if someone puts chewing gum into your hair. Freeze it and it will flake off.
Most have suggested using Ice & then a product called goo gone to remove residue.
I don't recommend taking it to the boutique, because there isn't much they can do. They'll probably just give you a quote on replacing the vachetta. It isn't a repair issue, it's a cleaning thing. Maybe call first before taking it up there? Maybe email Barbara at loving my bags? I would try scraping it off and try ice too and just accept that it might have a water stain. It's luggage so eventually the vachetta will have stains.
Ice will definately remove it. I had this happen to my leather shoes. Put an icecube in a washcloth or towel and let it sit on the gum until it gets hard. The gum should chip right off without leaving a watermark.