Troubled teen or should i be worried!

[pigglywriggly]

Hi,
I'm a first time poster on here looking for some advice please.
I'm currently looking after my niece aged 12 years while her mum (my sister) is away for 3 weeks on a much needed holiday.
I have niggling concerns about her behaviour while she has been staying with me. She is very clingy which is not normal for her, she follows me pretty much everywhere. She is normally quite independent even when she has stayed with me in the past. Sucking her thumb and carrying a tatty old blanket around the house.
In the past few days the weather has been very warm but she has insisted on wearing jumpers even in this sweltering heat. We went to a concert last night and my camera became foggy in the heat but my niece would not take off her jumper despite sweating profusely.
Prior to her coming to stay with me she was having problems with her mum which we all believed to be the usual teenage moody phase but her mum told me of promiscuous conversations that her daughter was having on Facebook. As soon as her mum found out about this, the computer was confiscated.
I only have one son who is in his late teens and have not experienced the mood swings of a young girl who is just at the beginnings of puberty.
Is this behaviour normal for a young girl? I do hope someone out there can advise.

I think it´s normal when i was 13 i never wanted to put t-shirts or anything sleeveless. I have seen this on other early teenagers as well but as Maryz says yes it can be a reason for self-harm and i would just try to take a look at her arms. But maybe she just has an embarrassing injury or a mark on her arm.

Promiscuous? my first thought could she be hiding a preganancy??

Just out of interest what is the " back story" to this?? Her mum is on a " much needed" holiday leaving a 12yr old for THREE whole weeks with her aunt ??

I have teens and have never been in a situation where I could feel I wanted to leave then for 3 weeks- I have left them for a week or long week end with grandparents and that is lovely but 3 weeks would kill me just bring away from them so there hasvto be something major going on....

Is mum actually ill? New boyfriend who she feels is more important than her dd?? Crumbling marriage she's trying to repair??

Something serious is going on- and that will affect you neice.

Anorexics also wear jumpers in warm weather (way they hide their illness, although you can train yourself to see how empty their bottoms & skeletal their skulls become anyway).

Anyway, I don't think it's normal, either (thinking back to what I & peers were like at 12yo). Theas18 has good intuition, methinks.