She takes fixed unit of slow release insulin in the morning. What’s basal bolus ?
T1 diabetics, who end up producing no insulin at all, typically take two types of insulin for a basal/bolus regime. The basal (long acting) covers their insulin needs when they are not eating (eg overnight) and then they take fast acting insulin (bolus) to counteract the carbs in any food they eat and sometimes to act as a correction dose if their bg is too high. This allows for flexibility in meal amounts and times, as you only need to inject bolus when you eat, and you can change the amount to cover the food you eat.
My guess is that your wife is still producing some of her own insulin so the doctors are hoping that her insulin needs can be covered by just a basal dose, and her own insulin will cover her food. If that hba1c is accurate it suggests an average bg of around 14 so it's likely that she could either do with adding some fast acting insulin to her system or to drastically reduce the carbs in her diet. Whatever she does, I'd recommend testing before and after meals so that she knows what her blood sugar is actually doing.
Her medical team should be helping her to get on a regime that lowers her bg, because running permanent levels of 14 or so will probably cause long term damage (eyes, kidneys, nerves etc). OK, if she's 90 that might not be an issue, but if she wants to have several more decades of healthy life (I've been T1 for 52 years and would like some more decades myself, if possible) then I would strongly suggest that she takes control of her levels and pushes her team for help.
Good luck to the both of you.