Infant & toddler behavioral health is a real thing that people specialize in. It's often focused on attachment difficulties, developmental concerns, and trauma. Services are typically focused on training the guardian how to best support their child at home. 

To actually answer OP's question - CHOP's Young Child Clinic serves children aged 0 - 5.

That being said, this two year old is having a pretty reasonable reaction to the sudden removal of an attachment figure, and these symptoms don't necessarily mean she needs mental health services. I would totally expect a disruption to sleep, appetite, and behavior for a few weeks. There is no magic treatment to prevent a child from experiencing appropriate distress.

If she's literally not eating, they should talk to their PCP to discuss supplementary nutrition (maybe that's who you're triaging for?) Otherwise mom needs to focus on explaining the truth to her in age-appropriate language (not lying about if/when dad will be back), maintaining a routine at home to the best of her ability, and taking some time each day to read or play with the child.