Have to agree far too early to do anything other than basic handling and wherever possible ensuring it is living as natural a life as possible i.e. turned out 24/7.
At that age lunging is likely to damage it's developing limbs.
Seeing as she's a rescue and underweight, it's doubly important that she's treated well - as the others have said, lunging is not suitable at this age. I would just have a gentle play with her when she's in. Pick up her feet, give her a nice groom, make sure you can scratch her ears etc. If she's feeling lively, you could lead her a short way along the lane and back, but I'd be slightly wary of going too far. It's important that babies this young get plenty of time to just "be"! You could try gently placing a numnah on her back or a surcingale if the owner wants to start "bombproofing" her perhaps...
I bitted Chancer at 18 months - he was getting big and strong and I wanted control from the start. I took him for plenty of walks, got him used to walking over things and having bags flapped round him, dogs, motorbikes etc. He was rugged, had his feet trimmed and good to do just about anything with. I also started getting him ready for showing, standing nicely and walking and trotting in hand.
At 2 years he was long reining and being led out from my old horse to get used to meeting tractors, combines, the local shoot, deer etc. He was also being shown so was used to loading, being bathed and standing tied up with no other horse around.
I did lots with him but only very short sessions - 10 - 15 mins three times a week and took everything very very slowly.
Mine is a very laid back sensible gypsy cob and mature in his outlook. Others need to be left longer before they can start doing things.
I still don't lunge as such, he is now 3, but I do work him round the whole school on the lunge with the odd 20 m circle and doing walk, trot and halts. He occasionally does a canter along the long side of the school.
I also started him doing a few trot poles and tiny jumps at 2 1/2 - always in the school so no hard surfaces which he really loves. We do this every few weeks just for 5 minutes and he is now doing 2' which is plenty for the moment.
her owner is very good with her she wants the best, shes not in any rush but is a bit clueless, should i advise her to leave working the horse untill shes nearer 2 1/2years old??
If by work you mean lunging, then yes I would. See Theresa_F's post - thats a nice amount of work for a baby to get to grips with and like she says, every horses is different. What type is she?
If possible leave as long as possible if weak from being a rescue the case it really would be best to leave her until she is 3. You can introduce all sorts of exercises as suggested above but if she is basically well behaved and not too big and strong her future would be best served by a little gentle disipline and a awful lot of chill time.
shes very fine and narrow, with long gangley legs!, the way she moves looks like she was bred for trotting... she came from a gypsy field.
shes very gentle
When I had my youngster I mostly just let him be, think it is the best thing for them.
Although we did "go for walks" following friends hacking so he saw all sorts of traffic,got used to grooming,baths,farrier,poped tack on ect and went to a few in hand shows for fun.
Diddnt start work untill he was nearly 4.
He turned out to be a very nice chap who the family that bought him are very happy with