She could be experiencing seperation anxiety at night which is very common at this age. In fact, I'm going through the exact same thing with my 11 month old. I'm sure not having her father around isn't making this stage for her any easier.
My girls haven't seen much of there father in the last month and we've also had a ton of other changes going on. Its really hard on both of my girls right now. In fact, my oldest just started wetting her pants. It is really breaking my heart. This might sound weird but my oldest is a total daddy's girl and when she was younger I would actually wrap her up in a tshirt that smelt like daddy whenever he had to leave overnight. It really helped alot.
Here is some advice I found on babycenter.com....
How should we handle nighttime separation anxiety?
Your baby's fear of being separated from you at night is very real for him, so you'll want to do your best to keep the hours preceding bedtime as nurturing and peaceful (and fun) as possible. In addition:
� Spend some extra cuddle time with baby before bed by reading, snuggling, and softly singing together.
� If your baby cries for you from his crib or bed, do reassure him and comfort him, but don't stay with him until he falls asleep. This will be painful for you both, but the results will be worth it. You'll have a child who can fall asleep on his own.
What if nothing seems to work?
Babies have different personalities, so some will have more severe bouts of separation anxiety than others. If your child can't be comforted using simple measures, it's time to reevaluate.
� Take a second look at your sitter or daycare center. Although you executed a thorough search before selecting one, the person or center may be a mismatch for your baby if he continues to become anxious and weepy when you leave.
� Leave your baby with a relative or someone he knows well for 15-minute periods, working your way up to one hour. Your baby can then learn that when you leave you'll return without having the added stress of being with someone unfamiliar.
� Reevaluate your goodbye pattern. Do you sneak out when your child isn't looking? Do you make it seem like you're going off to war? Do you slowly back down the walk waving and crying until your baby's out of sight? A simple "see ya' later, alligator" followed by a quick hug and a kiss can do wonders for an anxious child. Your actions show your child that leaving is no big deal and that you'll be home again soon.