dizzeeee, having a child who doesn't want to go to school is very tough (I'm speaking form experience)
Of course you are not being unreasonable making her go to school, but you need to be talking to the school about her reluctance to go, and try to get to the bottom of why she doesn't want to go.
When you friends say she might have "mental problems" I think they are probably just phrasing what they mean badly. School phobia is a mental health problem, as is depression. Both can occur because a child is unhappy at school. So that takes us back to why is she unhappy? Is the secondary school environment too overwhelming for her? Does she have any close friends to help her through the day? What does she most like/ dislike about school?
I would look, with the help of the school, and your DD, at how her school day can be made bearable, and go from there. If she builds up a a full blown school phobia there is no way you will be able to drag her into school, or persuade her to stay all day.
The bit where you say she doesn't like crows rings alarm bells for me, as this is exactly how DS was (is) and at times he had struggled(refused)to go into assembly. The school need to be aware of things like this so they can handle it sensitively.