Hi CountOssie - It's such a personal thing she really really really would need to try them on.
For good quality I always think "leather" but you might be limited in choice for leather with your budget. (I am always slightly gobsmacked at the price of boots.) You can sometimes get a boot with a leather "foot" and the leg bit is "other materials".
I would advise against suede or textile - gorgeous, yes, but yuk in the rain.
Also depends how "trendy" she is, for hardwearingness in everyday wear I would go for a low, chunky heel, not a thin or high heel - but your GF may not feel that way!
For comfort and hardwearingness, and warmth!, M&S are quite good (they have some good leather boots in their "outlet" section of their website, but only for very limited size range). Or Remonte Dorndorf [which you might find in a sale].
However, I am a notorious frump with high comfort standards, so they may not be a youngster's cup of tea!
On the other hand, if they are for Christmas, maybe you could give her a homemade voucher for "1 pair of boots" and go shopping together after Christmas when the sales will be on?
Good luck!