what to give my friend for her 18th birthday?  

I got my best friend:

£20 topshop voucher
A load of pretty tshirts from Primark
Bubble bath set
Cuddly teddy with ''18'' on it
Voucher for a really nice food place near hers for her & her bf.

Just make it a little more than you would have given to her in the past, you just need to recognise that it's an important birthday. You don't have to spend an absolute fortune on her though.

welcome to the wonderful world of mylot. its funny to think that you are the friend and you dont have any idea what to give her. i mean, i am sure you know what she like and dont like so that can be a start. well i am not much good in gift giving. my wife is the one good in shopping when it comes to gifts. a hand bag maybe, or a purse. or i guess something personalize, like a starbucks thumbler that you can change the logo into your own pictures. or you can personalized that by putting her wacky picture collection. something like that. i got that thumbler from my sister inlaw, that was her gift for me christmas and it was a 2 thumbs up. hope it helps.

I think the best gift you can give to your friend is your own made gift . I mean if you know how to draw then sketch him .. I find it more cute when someone gives you a gift that he's even the one who made it .. ..

hey hi kheigh.so its your friends 18th birthday....it sounds really great.
So you both have been friends for around 4 years now..wow that is real nice.
I guess you try giving her something she could preserve, something as a gesture of rememberance, which when you see later in your life then you can recall this very day and refresh all your memories.You try creating something of your own rather than buying readymade stuff.May be you can try assemble all the great pictures of you both together all these years and put it in a album, giving caption to each and every picture.I am sure she will just love it.
There will be a lot others ideas too,just think it over i know you will choose the one which will suit best to you and your friend.
Happy mylotting.

Don't stress so much that this is going to be a formal debut party. The goal of the present, to give her something she will enjoy and be happy with, is the same. When you go to pick out a present for her completely ignore that it is a formal event, ignore that it is for the 18th, just consider her and what she likes. As long as the present is bought with her in mind it is unlikely you will go wrong.