I guess some people handle illnesses better than other people. And you are right, when she's not feeling well, it's no excuse to treat you badly.

Maybe it's time to realize that when she's not feeling well, she's certainly not up to being amiable to helping someone with something and it's best not to ask her for help.

You can always wish her well and tell her when she's feeling better to email you and you can both get together over lunch or a cup of tea.