Exactly, onlyboys. The idea that "work" and "play" are two separate ideas is a wholly artificial adult imposition. For children, play is their work. That doesn't just mean that silly, creative, fun, goofy play is everything that kids should be doing. It means that children are constantly learning, absorbing, exploring, and that is both play for them (it's fun!) and it's also 'work'. A child who is wholly absorbed in a fascinating activity is a sight to behold... their level of concentration and seriousness can be shocking, and then when they're done they say "THAT WAS FUN!"
I also wholly agree that we should "let kids play" and not IMPOSE work on them. But we also have to realize that there is less distinction between work and play in a child's eyes than in ours. Not until WE impose this distinction on them does it become an issue. Having "work" available for children when they want to do it is just fine... if it's something they enjoy doing, then it IS play.
"Let kids play" also doesn't mean "never give them any suggestions on what to do." Child-directed means they choose what they do, but you can still make suggestions, especially for new activities they don't know how to do yet, or that they have the option to choose.
The other day, my daughter decided she wanted to clean the walls. I think she was watching Blue's Clues and Steve was spraying the pawprint clean.

She went and got the cleaning spray and a cloth and asked me where she should clean. I showed her lots of dirty walls and left her to it. To me, that would be "work". To her, it was play AND work.
When she was younger we were very Montessori-inspired at home. (Now she's almost 4 and I'm still very informed by Montessori principles) I did buy a few items, which we love, but we focussed a lot on the Practical Skills areas, as has been suggested. A 3.5yo is VERY ready for helping with cooking, setting the table, sweeping the floor, helping with laundry, washing windows, etc etc etc... they LOVE to do it.
In fact, the Montessori school environment is designed to be home-like, and imitating what a child would otherwise be doing at home in ideal circumstances (Dr Montessori's first schools were for underprivileged kids with terrible home life). So there's absolutely no reason to separate what they're doing "at school" from what they're doing "at home". She's likely already used to helping with food preparation and serving at school so it would be totally natural. And in fact, I think it really SHOULD be done at home... those sorts of skills are learned NOT just for use at school, but for their whole life OUTSIDE of school as well.
Anyway, all that applies to the Practical Life skills. I'd agree that if she's doing Montessori work with the more expensive materials, etc, at school already, then there's no real reason to do a lot with that at home. If she's ASKING for it... well, maybe look into some homemade alternatives. And don't worry about the presentations or lessons -- just let her work with the materials the way she's learned and is used to at school.