I need advice from another mama!?

I just started babysitting a 13 month old and I was shocked when her mom told me that she only took 1 nap a day. Well this is my 3rd day watching her. She falls asleep in the high chair during lunch. I think that is a sign of being too exhausted. Today I put her in my room in the play pin so that my 10 month old could take her nap and there would be silence as she was trying to go to sleep. 10 minutes later I walk in and the little girl im watching is sleeping. Should I give her 2 naps a day and tell the mom my reasoning or should I just continue to give her one nap a day? The mom works 60 hours a week and isnt really around her daughter that much. When I asked during the interview she couldnt even tell me her daughters schedule. The only thing she knew was 1 nap a day.