What Are The Side Effects Of Insulin?
little weight gain...
the most common 'side effect' is weight gain. Don't expect too much though (a couple of kilos or so). Insulin is not given for weight loss. There is absolutely no such indication. Insulin can only be given for insulin-dependent diabetes mellitus.
Using insulin may cause other problems like skin problems at the site of injection.
In conclusion the most likely side effect is insignificant weight gain. If insulin is needed it would be beneficial for her health.