Get her something that isn't showy. Sure Tiiffany and all that have the name and the style but then, "hey look, it's yet another guy who went to Tiffany's."
Go for something really personal, really think hard about this woman and what she means to you - spend from the heart with no thought about whether you will get any kudos from the gift (not that I'm suggesting that this is what you are thinking but you really have to be selfless to try and figure out the best thing). Has she been stressed lately? - what about a full day spa treatment? Does she enjoy cooking? - maybe a course at a cooking school? Does she like music? - perhaps concert tickets?
Sorry, I just find jewelry, gold, silver and all that stuff to be a bit clichéd and OTT for a present. Yes it has it's place but only for the truly special times. Forget matching the price of gifts, it just leads down a bad path, a present that shows you truly care and understand her is far better than an expensive gift that you picked off the rack in 15 minutes at some high-fallootin' jewelry shop.
Out of the suggestions you have given, I'd say the jacket - CanadaRAM has it right, cold hands inside your warm jacket (especially in your neck of the woods, BRRRR!!!!) is not a wonderful thing and if you get her one of those big fluffy warm ones with a decent collar you can go on walks in the snow and she'll get that beautiful, snow dusted, pink cheeked happy glow about her.... hmmm, that's it, I'm sick of being single...
Good luck, hope this helped a little, if it didn't, ah well, it's only my opinion anyway.