Re: She has a point
1) There is something bad that is likely to happen (e.g. death from lung chancer); your actions may well be adding to that bad thing happening (smoking) ... but if you stop smoking the bad thing may well still happen; you may still die of lung cancer. The chances are lessened but not negated. Something else may give you lung cancer, something completely outside of your control.
2) You will have to change your behaviour now and you will not like it (e.g. giving up smoking) - to greatly reduce the chances of the bad thing happening.
3) However, even if you do stop this particular bad thing happening, other bad things are still going to happen. If lung cancer doesn't get you something else will ... you are, in fact, still going to die.
Back to climate change...
Even if we do manage to maintain the Earth in its current chilly state, so desirable for human life, for the time being - it can't last. If the human species survives long enough to evolve into something else, that something else will, by definition, be able to cope with the planet in whatever state it's in... otherwise it will have gone extinct.
In the past this planet has both been much hotter and much colder than it is now; life has carried on. There's still a couple of billion years for life to adapt before the planet becomes inhospitable to any form of life.