How do I get my girlfriend to enjoy being outdoors?

She's had next to no experience of being outside of a city before we met, and while she's been a real trooper about it and adamant about not saying that she doesn't like something before she's tried it, it's very obvious that she just flat-out doesn't like it. I keep telling her that I don't want to force her if she hates being outside, but she keeps insisting that there has to be SOMETHING outdoors that she can tolerate so that we can do things together.

We went ice fishing last week. She's not a complainer, but the whole time there she sat quietly looking like a wet dog (exhibit A), just utterly miserable, patiently waiting until we're done. Every time we're doing something outdoors, she always looks like she's in pain, and is just quietly waiting for it to be over.

How do I get her to like being outdoors? I want to take her camping one day and she insists she can't tell that she won't like it before she's tried it, and I don't want to spend three days in an otherwisely nice campsite watching her quietly have the three worst days of her entire life.

How do I get her to enjoy it more?