first off, im sorry for your loss that has to be so hard, and i could never imagin it!
of course.. i mean i wouldnt call it depression.. but she can feel somethings different and she can miss him in her own baby way... shes a twin, they can feel those types of things... sadly i really dont think theres much you can do about it that will give instant results.. but as your probably already doing, just give her lots of love and attention and let her know you love her. Im sure she doesnt understand whats going on at all, but its almost like a comfot, like a blanket or pacifier was taken away, just in a way bigger way... im sure she knew he was there and now she doesnt hear him or see him anymore and misses that "comfort"
thats the best you can do... shes to little for u to explain.. obviously...
the best u can do is show her how much u love her... and wait it out... maybe keep one of his blankets for her to use..even thought she might not undersand now, later down the road you can let her know that blanket is her brothers and im sure that blanket will turn into her confoft thing.. like i had a blanket i still keep with me and im 17 lol it can be her one special blanket. hug her, kiss her, cuddle with her and let her know her mommy loves her... she can sence the love from you, just liek she can sense something else is wrong.
I am very sorry for your loss! Give her attention. Maybe find one of your friends with a baby about her age and have then together a lot. Keep his stuff around the house for a while. They have been together 12 months [since conception] She probably misses her brother. Give her tons of attention and love. She should eventually go back to her self. But she will still know that something is different.
I'm so sorry for your loss, I can't even begin to imagine what you are going through. Hold her and give her lot's of love. Talk to your peditrician the next time you take her in. They might be able to help you if she's not doing any better. Again I'm so sorry you are having to go through this.
try letting her look in a mirror. twins have always been together, they were in the womb together and they are use to it. thats why typically people keep twins together (same crib at first then same room etc) at such a young innocent age she doesnt understand why he is not there. she probably feels lonely and possibly abandoned. thats where a mirror and maybe stuffed toy would come in handy. she can see "another" baby and play with/feel the stuffe toy
im so sorry for your loss. and best of luck with your little girl
if you dont mind, how early were they and what caused this terrible event for youir little boy? (if you dont want to say thats ok)