K.,
Your baby girl is going through a HUGE adjustment right now. It would be like us moving to another country without our friends and family. You are doing the right thing by allowing her the lap time and falling asleep in your arms. This is the most safe place in the world for her and she is telling you, "Mommy, I feel relaxed and can sleep now."
It normally takes 10 consecutive days for a child to adapt to a new sleeping schedule. The best thing you can do for her right now is provide as much Mommy time as possible. Allow her the comforts of working into this new sleeping schedule. It will change the day and night sleeping, but in the end, she will be on a new schedule and the happy little girl you know and love dearly will return. You can even talk to her about the new sleeping schedule. SAy something like, "Sweetie, I know it is difficult to sleep without Mommy around during the day. But, please know that I am thinking about you and sending all my lullaby kisses your way." Children this age can not tell you what they are going through, so it makes it that much more important that we give them as much loving words as possible during transition times.
One note, if you miss a childs first "sleepy signs', they will move into second wind. This will put her way passed bed time schedule and cause her to wake even earlier. It definitely is a balancing act and Mommy is definitely the only one that 'Knows Best". Go with your instincts....Good luck!