well i have a 19 year old boy and 17 year old girl and 15 year old girl and a 7 year old girl, it will pass, my 17 year old is now my best friend my 15 year old is like your daughter, i just do not give up and i always sit her down and tell her she can speak to me about anything even sex if she wants, i do not always get through but i never give up trying, my son is now the man of the house as my husband just woke up one day and walked out, my 7 year old is too old for her age and is more like my 15 year old, but i just keep telling her i love her and mum is always going to be here for her, im am so proud of them all, just show the love to them, even if you are finding it hard, trust me you will have a best friend in a few years