Try not to worry too much. I was a pretty cold fish with my mum for years but we recovered.
I agree with the small things. Is there a job she hates? Ironing? Cleaning the toilet? Do it without asking and keep doing it. Remember your job is school so don't aim to take on the whole world but just pick something which takes a load off your mum.
I worked with my mum for a wee while and it really helped me 'get' her. I took to making her packed lunch (nice, varied fillings) and occassionally left her a wee note just to say hello)
Yes to the hugs. Share your chocolate. Ask her how her day was. Talk to her about something that doesn't centre on you, take an interest in what she likes or does. I have one who does all the above and another who does the hugs but apart from that I appear to annoy him by existing.
As the parent of two teens myself I agree with Foggles that a big hug, tell her you love her works wonders.
You sound busy with exams etc but sometime simple easy acts of kindness mean a lot- noticing that the bin needs emptying, making a cup of tea and taking it to her without asking, being in kitchen and noticing dishwasher needs emptying. Laying the table and lighting a candle for a meal. Simple stuff but it all means a lot- it says I am thinking about someone else!
But you sound a lovely teen anyway to come on here and ask us!
If you're a parent of a teen, you will love them dearly. However it's probably also true that your teen has little niggles that really annoy you.
I've recently had an argument with my mum (I'm 15) and I want to make it up to her by being a bit more lovely. I'm stressed at the moment with exams and such, so I'm not the loveliest person to be around!
So I was wondering, what little things would you like it if your teens did that would bring a smile to your face?