We have three children in two different Montessori schools. In my experience Montessori is very good for gifted children, especially if they enter at the younger end of a mixed age classroom. Active support for gifted children varies not only from school to school but from teacher to teacher.
We have had one teacher who has been immensely supportive of DYS, providing advanced lessons and enrichment, and supporting his going for math lessons to the highest class in the school (a 5 grade acceleration). We had another teacher who flatly told us - when we told her DD-then3 was reading simple books with sight words - "we don't expect three year olds to read" and refused any enrichment. We switched DD to a different classroom, where her teacher does provide advanced work to DD and a small group of gifted peers but does not go out of her way to challenge or stretch them. DD is fine with that but is cruising along and could do with a bit more challenge when she switches classrooms. The gifted group is working about two grades ahead.
We also have a two year old in Montessori program where I spend a morning each week. At two the curriculum primarily focuses on practical life, emerging language, fine and gross motor skills, and social interactions. It is very different from most daycares for two year olds, and from most traditional schools. If your child is engaged and happy with the activities I would not push for more formal academics. (DS had to "go back" as a kindergartener to master a lot of practical life activities most three year olds have learned ... he was too busy reading and doing math at that age) The works in the classroom are typically updated weekly, and as the children get closer to three more math and language activities are typically incorporated. Our DD2.5 is readily included in these activities with the young three year olds in her class. A good teacher will gauge your child's level but may still have them work through all the material, since most works are designed to address multiple developmental areas. (e.g. sensorial as well as math). Perhaps worth noting that it is common for children in Montessori to read ahead of age peers in traditional schools. Also, Montessori tends to teach writing (tracing letters at first) before reading, but is not rigid about that sequence.
Another very important note about Montessori is that the children select their work. The teacher may suggest something, but ultimately the child decides what they want to work on. Again if your child is engaged and happy she is bound to be learning, though it may be more in the practical than academic areas. As in your daughter's case, our child's teachers realize that she is bright but probably don't realize just how bright she is. At home she works on more advanced math (if you can call it that - counting and adding objects) and reading, and I have no doubt that she will jump from reading sight words to actually reading before long ... but having been through this with DS I am not in a rush! There are a lot of very useful things to learn about navigating the world, independence, and peer relationships: that is the real value of toddler Montessori.
On balance, we are very happy with how Montessori is serving our children. In particular, pre-K through early grades seems so much better suited to gifted children's interest, learning style and pace than most traditional schools.
