Which horse should my father give to my little sister?

If your father knows anything at all about horses he would know that there is no possible way any child no matter how small could sit on any miniature horse, incidently anything that is to small for a lightweight adult to sit on isn't going to be trained anywhere close to the minimum standard needed for a kids pony. Does your sister have any riding experience? Unless she's having lessons at least once a week, can walk, trot, canter, manage a small jump comfortably and there is a responsible experienced adult rider to hand at all times to keep her right she has she has no business owning a pony.

Unless of course your parents are willing to pay to keep it in livery where there will be people on hand who can provide these need and give her regular lessons on her own pony which she will need anyway regardless of her ability, have your parents considered the costs at all?

Livery is upwards of €75 per week - thats basic do everything your yourself and not including lessons it may not even include a stable!

Lessons - on your own pony upwards of €30 a lesson depending on how good the instructor is

Farriery - Up to €70 (depending on the pony) every 6-8 weeks

Then there's feed, vetrinary fees, insurace, riding gear (which must fit properly and she will grow out of very quickly at her age) eg. At her age she'll need a new helmet every 6-12 months or everytime she falls on her head at an average cost of €80 a pop. Then there's travel costs, entry money for shows if she becomes so inclined (she'd need to be for such an expensive hobby!) clinics, stable manangement and safety training, the cost of schooling/reschooling the pony . . . . and so it goes on.

I have 2 kids ponies here that there was absolutely nothing wrong with untill unknowlageable people got their hands on them and ruined them. There are enough ruined ponies in the country, please don't create any more as this makes them completely useless and most end up in cans of pedigree chum