My common law partner left tonight while I was away from home with our baby girl?

So my "wife" left with our baby while I was away all she left was a fb message that I coulnt get untill I came home and found out she was gone and I called her to figure out where she was . She said nothing exept to check the message she left. In this message she says she realises that no one is happy and so she is moving to her moms. Also she says that she is not trying to take the baby away and she wants to split custody 50/50. And thats it. what bugs me the most is that today was a good day there were no arguments no fights nothig that would provoke her to walk out. Not even a hint as far as km concerned we are working it out. Now we have had some arguments about rrelatively petty things like I dont get her flowers often or take her out or in other words romantic things. I on the other hand am having an argument about living conditions like the fact that she is too messy or when she does anything is very mediocre at best. Just to give a background story, I work early mornings, as a school bus driver, I get a break in between runs so usually I take a nap for a while and im back by 430 from work. she works 4 to 12 doing online support. She leaves to work before I come home so during that small time frame my mother takes care of baby and then I take over when I come home sounds like a perfect arrangement. In the mornings she wakes up with baby around 9 to 10, makes baby oatmeal but lets baby basically eat by her self, I come home on my break about that time. she makes what she calls lunch wich is protein and rice nothing else takes baby to the park for 20 minutes comes back and "plays" with her ( wich means turn on tv while she plays with her phone) gives her some soup usually made by my mother and puts her down for a nap and then off to work and she is done until the next morning. When I come home I just play some didactic games with her give her some fruit, dinner, give her a bath, put her to sleep. Any ideas? What do I do?