anyone from Paris ? need help for tonight

My younger sister is arriving to montparnasse this evening, she has to go to Roissy - her plane is tomorrow morning, she's going to Corse.
I don't know if she can find a hotel around montparnasse or around roissy and it will depends of the RER hours too .... i can't do anything for her from here, because she's with her bf and two other friends, i have the kids and i only have a 5 places car !!! so with their suitcases ... i don't have space for them in my car and i haven't found anyone to look after my kids then i could go and pick them up in Paris and drive them to the airport tomorrow morning ..... i'm angry she didn't organised all this better, SO
anybody knows where they could stay during the night ? montparnasse or roissy, not so secure if you have an idea, thanks for telling me, i'm doing my best calling lots of friends in Paris, but for the moment i haven't found anybody, i guess they're all on holyday .....
i know it's not something we can ask like this, but i'm just worried for her, i don't like Roissy or Montparnasse at night ! please if you have an idea ...... pm me ! thank you