Mother Of My 2 Kids Left In The Middle Of The Night.

Hello everyone i am 29(M) my fiance 25(F) have 2 kids together a 6 year old girl and a 3 year old boy. We live in florida. Today after my fiance got home from work, she said she was stressed about our relationship and made comments that she did not want to be with me anymore. While i was sleeping with the kids she left at 1 AM. I am scared of losing my kids. I own my house im the only name in the house. She works technically for me as she works at my parents family business. Her mother lives in a 1 room trailer and so does her father. Please advise me on what to do.