Personal politics apart (and it's irrelevant to tell you what she plans to do with her own children), I think teachers are on a hiding to nothing discussing this with parents. The teachers at our primary school are generally supportive, but never keen to discuss an individual's chances.
You need to know what sort of system you're in: fully-selective with 25% of all children getting in to grammar schools, wildly selective with 10 children fighting over every place (and that's for every 10 who decide to go through the proces, not every 10 in the school system), or somewhere between the two (as where we are). I have one child in a local grammar, and one who missed the mark by some way this year, in spite of being level 5 for Maths and English. Roughly speaking, the top half of the class here tend to take the test, with between 20 and 30% of the class getting a place (this is in a very high-performing, middle-class school; there are probably grammar places here for about 10% of the school population generally - it's hard to be sure, because the catchment area crosses two county boundaries).
If you are thinking about using a tutor, ask them to come and assess your child's suitability. If not, get hold of some suitable books and decide for yourself. If you are rational and realistic yourself, there's no harm done by letting your child take the test and getting your answer from that. A degree of extra tuition, whether you do it yourself or pay for it, won't hurt, and education is never wasted. If your child hates the practice, that might in itself be an answer to the question of suitability.
The 11+ Forum is the place to go for information on your local test. Don't be put off either by horror at the lengths some people go to to get their children in, or by people saying you shouldn't prepare at all (because other people do, it makes it difficult not to do some sort of practice).
I don't think it's a great system myself, but if you're going to go for it, do it with as much knowledge as you can of your own child and the local situation.