Curfew for DD16

[namechangeforthis234]

I thought I was being reasonable saying she had to be home from hanging at the park with 5 of her friends before dark. I gave her a 9.30pm curfew, but apparently 'all her friends' stay out til whenever they want and tend to be home about 10.30.
I've been single parenting her since she was 12 so have no-one to discuss this with as her dad is hopeless and far more interested in himself.
There's only 2 other girls in this group, one of who has a complicated home life and does as she pleases and one who is the youngest of a big family so her parents have all been through this before and are more chilled than me about everything!
I told her I'd rather be wrong and risk her being cross with me than be wrong and risk her safety, but am I being unreasonable?

[sleepismysuperpower1]

have a read of this, you might find it helpful x

www.netmums.com/coffeehouse/being-mum-794/tweens-teens-61/1015360-help-what-time-reasonable-nearly-16-year-old-allowed-out-weeke.html