Most do, but not everyone's.
The same way you make a guy's nipples hard.
Because you're horny?
Because their horny and so excited
It means you're horny or have chills.
It is when somebodys nipples are hard from either being cold or even horny. It is also referred to as "RT"
OK first of all I wanna kill the myth that womens nipples get hard when they're horny - they don't. Second, we don't want you to know! That is one of the perks of being a woman - we can enjoy it in peace without anyone medling. Maybe you can see her get more red around the cheeks but we can hide it.
To make your nipples hard, you need to sexually stimulate yourself. Massage your boobs, rub them, squeeze them, etc. Also, flick, lick, and touch your nipples as much as possible. Your nipples will get hard once you're horny and sexually stimulated.
No, it doesn't. It means you are horny or you're cold, or you want to have sex or masturbate. It's normal.
If it is he's sucking too hard. Womens nipples are more sensitive then mens.
when they are horny
If you mean that they are always erect it is normal and nothing wrong with you.
Flick them, get cold like in a cold pool or super hot like in a shower. Or when u are horny they'll get hard (if you are a girl)