I need help!

So some mornings oddly enough the morning after my partner has had her for the day. She will wake up being sick. At first I put it down to teething as she shoves her fingers down her throat. She will then have a very very bad poo so I think oh she has a bad tummy and take the day off work to look after her but she’s absolutely fine after she has got the sick out and one bad poo she’s fine no more sick and normal poos. Any advice? Last weekend she was actually sick as she was sick for 24 hours straight but most of the time it’s once and she’s good to go?