Married before 18

[changednamefort1]

DD(8) has a friend from an Asian background and we often see her walking after school. She went on holiday for about month and half including school holidays and school days. So we were just talking and I asked her about her holiday and she said they had her sister's wedding and it was really fun. I've seen her sister before and looked very young, so I just asked (out of curiosity) how old is her sister, she said she's 17

Should I do anything about this information??
I do have few concerns about the mom.
DD s friend who is also 8 walks alone after school for about 10 minutes, crosses a main road and goes in to her Mom's friend's house till mom comes to pick her up.
If mom's friend is not available she waits by the side of the road alone, this makes me really uncomfortable and few times we've waited with her till someone picks her up. This have taken from 5 minutes up to 20 minutes waiting.

I'm unsure what to do should I just ignore it.

Marriage with parental consent is lawful at 16 in the U.K. And yes, the young woman’s age and the fact that the wedding took place abroad could well indicate that this was an arranged or at the very least assisted marriage; but there’s nothing illegal which has taken place unless there’s evidence it was forced.

The issue with the younger DC is entirely separate. It isn’t an ideal situation and maybe share your concerns with the school that she’s sometimes left waiting in the street on her own.