Am I being unreasonable?

I currently work in hospitality a supervisor earning minimum wage (£8.21) I’ve worked in the role for 17 months and I’ve never been offered any kind of pay rise for role I do. There’s a girl I work with who’s younger than me but since June she’s been working in the same role as me. I’ve just found out that instead... show more I currently work in hospitality a supervisor earning minimum wage (£8.21) I’ve worked in the role for 17 months and I’ve never been offered any kind of pay rise for role I do. There’s a girl I work with who’s younger than me but since June she’s been working in the same role as me. I’ve just found out that instead of earning the £6.15 that’s minimum wage for her age she’s earning £7. Am I being unreasonable to think that if she’s being paid extra then I should be too?
Update: I haven’t found this out in an sly way. She’s openly told me as we’re close friends.  
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