Tooth Decay-Tarter-Plaque?

So my friend has never been to the dentist and I'm trying to make her go. Money has always been really tight. She came to me the other day stating that she was scared that her teeth might be rotting. She said every time she brushed her teeth it bleeds (she does no brush her teeth very often..) Yet her gums are pink. She said after a while of brush it does stop. But if that place is like picked at or so it bleeds kinda bad.

But she said she had noticed on some of her teeth in the cracks inbetween slightly up close to her gums there is like black? light black. Shes worried that this might be decay? But it's weird because I thought when you're teeth decays it starts at the top of the tooth not the cracks, or can tooth decay be anywhere?

I keep telling her it's probably bad tarter build up since she doesn't really brush her teeth very often. That a good clean should do it because she has plaque in places as well. She said it doesn't hurt either.

What do you guys think?