Yes, but so much harder when it's something I care passionately about (Do I tell the girl who bought the home dopplar that it uses a technology that emits radiation? I know she got it for her peace of mind, but she COULD have no idea that it's probably not wise to use it everyday for long periods of time. And that sort of thing.) Then it's just compounded by the fact that I'm already making very different decisions that can come across non verbally as judging (even when the decisions are personal and not a judgement on anyone else at all). It's just tricky. But so far, so good!
Oh, and the down side to wearing maternity clothes--I got touched on the belly THREE times this weekend by non family members. Hmm. Maybe I should switch to baggy sweaters!
I think, personally, I would give her as much information as possible so she could make an educated decision for herself once she has all the pertinent information. I might say something like "Oh, being able to hear the baby's heartbeat at home is exciting/reassuring. I know there's some controversy about it, how are you feeling about the issue of exposure to radiation?", and if she doesn't know, then you have an opportunity to tell her.