you can buy good quality cockatiel /parakeet mixes from any petstore,
the bird may favour the millet or it may favour the sunflower/safflower seeds,
if it turns out that it is the sunflower seed it favours then cut them out of the feed by just feeding mixed millets as the sunflower seeds are very fatty and can make it ill..
because the bird is brightly colored doesnt mean it is a male , you can get brightly colored females, if i knew the body color and also the color of its face it would be easier to say what the sex is or as some mutations in cockatiels are impossible,
both male and female cockatiels can talk although males learn a lot easier than females and speak clearer and hold more of a tune when whistling,
personally i dont condone the clipping of birds wings and if inexperienced with clipping of wings then your best bet is to take it to the vet to have it done, this way he/she can show you the right way to do it so you can do it yourself the next time.. all the sites in the world can give you a guide but what they cant do is to tell you that you are doing it wrong!
i will dig out a link i have somewhere on wing clipping but really i would say that it needs to be done at the vets...i dont agree with the clipping as even when clipped the bird can still fly, it just cant gain a great height although it has been known for them to fly upto 12 feet plus with clipped wings.. and for long distances, it makes them clumbsy and they bash into things which can hurt them and it knocks all their balance to pieces..
nail clipping is easy to do if the birds nails are clear or pinky color , if they are grey nails then they are harder.. if the nail is clear or pink you can see the vein inside the nail, this vein must not be cut into,
if it does get cut into and the nail starts to bleed you should pad the nail with corn flour to stop the bleeding and help it to clot... dont panick to much if the vein is cut into as it is an old wives tail when they say that just a couple of drops of a birds blood can kill it .. so ignore that.. birds are hardier than we think...
as for beak clipping then i would say that is also a vet job also !! if the beak is clipped at the wrong angle and pressure put on the wrong part of the beak it can crush the beak so is not something id recommend trying..
if the beak is slightly overgrown from the tip then this can be done by holding the birds head steady and using an emery board (nail file) very gently and shouldnt take long to do..
i wish your sister the best of luck with this bird and fancy finding it in the mountains

lol
bet she was quite surprised lol
i will have a diog round for some good cockatiel books with a lot of info in and send you the titles ,
in the mean time if your sister has internet access i would recommend these 2 sites
UK Birdkeepers Message Board (Powered by Invision Power Board) and
Flockintiels; Cockatiels Budgies and Finches.
both will be able to provide you with info needed however flockintiels can take a while to answer any questions as not many people seem to post on their ...
good luck
katie