seperation anxiety with 2 year old after split with my husband

My husband decided to leave me and my daughter while i was 34 weeks pregnant. but 2 weeks ago i gave birth to my second daughter. i need help physically taking care of both of them. i asked him if he can our two year old for the day after not seeing her for almost 2 months. ever since he left almost 2 months ago, i feel she developed an overly attached relationship with me. she cried uncontrollably with him until she vomited and fell asleep.. he had her for no more than 40 minutes before he brought her back to me. he blames me 100% for it all, when i been asking him for help since the day he left... he never showed up. has anyone been thru anything like this? will she get better? how can i help her with her seperation anxiety? i dont know what to do or where to start? should i start now or give her a couple more weeks? i need to go back to work in about a month and im worried.