Maybe not mixing enough to get the air in. She could try and electric whisk or mixer if she find it hard to mix it long enough.
I have arthritis and struggle to mix it well enough on my own so am thinking of buying one.
Does she use self raising flour in cakes (if not using normal flour may be the issue) or not letting the bread have enough time to rise before baking.
When in the office the door should not be opened and nothing should be slammed as this can cause it to stop rising.
Is she baking them for long enough, maybe the centre doesn't get cooked properly. If so then baking for longer on a lwer temperature may help and checking the middle with a thin skewer to make sure the middle is cooked before removing from the oven.
If it needs a longer bake but she's scared of the top burning then a lower heat for longer as said above and she could use some foil over the top to stop the top getting so brown early on and she can then just remove it for the last part of the bake.
One idea for cakes (passed on by Mr's J's lovely auntie the other day) is to put a normal spoon full of water in before the flour when baking a cake and a bit of bicarb of soda.