It's an issue of consent. She's voluntarily sharing specific selected photos & videos with her social peers, a hacked baby monitor would be a violation. The glib dismissal here helps nobody.
Her baby hasn't given consent. Believe you me, there's loads of 'Invasion of Privacy' lawsuits from kids to their parents coming down the pipe over the next decade.
I think it's the same for these kids who have been posted on social media by their parents. Kids get their lives ruined by this type of stuff. The internet has a long memory, and these children are in no way capable of consenting. Yeah it's not Cash Me Outside girl bad but you're still potentially putting still maturing children on display to be potentially mocked by random internet mobs. Forever.
The distinction between sharing specific photos and hacked baby monitor, as pointed out by ianlevesque, is still important and it's wrong to casually dismiss it.
and what did you tell her?
"Baby" gadgets and toys are the most vulnerable. I liked the story where a teddy bear that allowed parents to leave messages was hosting recordings and replies on a public fileserver. You have to get more imaginative to think about who would take advantage of that and why, but its a valid enough answer, especially for a simply "spying" concern.
So, of course I helped them to setup the IP camera in such way that they could use it securely. (VPN, strong encryption on their WiFi, etc)
And of course I also explained them that they should be careful with whom they share the photos.
My sister had a baby last year, and she's been posting and sharing photos and videos non-stop.
Recently she asked me if I knew if hackers could break into baby monitor because she was worried some hacker may spy on her sleeping baby... I had a good laugh first, then I felt sad for her.