My daughter is also 5.. DH died two years ago. She will throw out "I miss Daddy," "I wish Daddy could be with me", "I wish Daddy would see our house" and so forth. She does domit at nite to stall sometimes, but that is usually, tell me a story about daddy. Kids are so much smarter than we give them credit for.
I agree this solo parenting is so f-ing hard. My frustration with her is just temper tantrums, yelling back and at me, sassy talk, etc....what most view as normal kid stuff but I always have to wonder if it's normal kid behavior or a way she is dealing with frustration from not understanding why her dad isn't here.