Please do not let her cry it out at 7 weeks old. Crying won't hurt her, but she only knows instincts at this point in time, and crying is her way of letting you know she needs something. It might be food, it might be a diaper change, it might just be the comfort of being held and comforted in this big, scary, cold world unlike your womb.
My second child was "grumpy" - I wouldn't go as far as colicky. I was really worried about day care, but they're pros, and she did great despite my fears. I was also diagnosed with cancer my 4th day back to work after maternity leave with her, and sometimes, not knowing if I would survive, holding her and knowing she needed me was the only way I could get through the day.
I'm not a lenient parent by any means, but with infants, I think we need to realize they don't understand and only act on instincts. My guess is that she's either cold, has reflux, or just needs the comfort because she can't soothe herself right now.
Good luck getting back to work.