If your mother is a fanatic who can't be reasoned with in that regard, then it's probably best to ignore the matter. Otherwise there'd be a risk that she ends up convinced that your thoughts are controlled by "them" (tm), nd that doesn't bode well for your family life.

If she's open to discussion, then you can try to shake her faith in the conspiracy theorists. The best way to achieve this is usually to discuss trustworthiness of sources, ease of faking evidence, the scientific method, and reliability of "peer-reviewed science" vs. "purported quotes of authoritative figures". Once a conspiracy theorist has realized that it's much easier to create a fake conspiracy theory as it is to create an actual conspiracy, he/she has a harder time justifying their belief in something that stands on very shaky grounds. It's possible to convince people this way that conspiracy theories are, well, just conspiracy theories - but it's _a lot_ of work, and quite difficult.

The main advice I can give you is to not present science as a monolithic truth (if you do that, then any discussion just degrades into a battle of beliefs), but to instead explore, together with the conspiracy theorist, ways of reasoning and their reliability.