Newly diagnosed 3 y/o going hypo at night

Hello all. Our 3 y/o was diagnosed last week. Every night since, she has hypo'd up to 5 times a night. Each time we have to bring her sugars up with fruit juice whilst she's half asleep, only for them to plummet the next hour again.

We've been in hospital for almost a week now and I'm so stressed.

Once she's had her evening meal and fast-acting insulin about 6:30pm, her sugars go up as expected, and then start coming down, but they just don't stop coming down. They don't slow or level out, they just plummet until she's in the 3s and we're having to get her back up again. Then repeat all night.

Any tips? We've changed her ratio for her fast acting (Fiasp)to 1:35 as they think she's super sensitive to it. We've also changed now her long-lasting Trefibo to 2 units instead of 3? But we're following the same pattern tonight. I'm terrified for my poor girl and don't understand why we can't stabilise this.

Thanks