Nausea and gas in 6 year old. Grateful.

My daughter is 6 years old. Weight 23 kg. She has been complaining of nausea for the last couple of days on and off. No vomiting. There's always gas after she feels nausea. This morning she had nausea as soon as she woke up, had gas. She said mild tummy pain for about 5 minutes. She eats only home cooked food. She's lactose intolerant so doesn't have dairy at all. She said she felt better after sometime. Her poop had been normal. 3 days back it was a lighter yellow but was back to normal yest and day before. She also has a bit of cold and very lil phlegm between her nose and throat. I'm not sure if the nausea is due to the phlegm or stomach issue. She coughs once or twice a day and has no sneezing. I have not given her any meds yet. Her regular meds are allegra nasal spray once a day,  seroflow in the night.  For the may few months duev to adenoids enlargement. Pl advise if I should wait and watch, what the reason could be. I would be grateful. Thank you.