No it is not,you should be as rude as you like to her now for that little observation that she pointed out.
For instance I have someone who follows me around the net acting out the role of being my special ghost friend,like the shmoo,but to that person I would say it is a sure bet that they feel like crap when they log on to find all the emotional abuse I have left for them to read.
It's only fair if someone tells you exactly how they're fucking with you for you to do wild and totally atrocious things back to them.If you don't then the relationship power dynamic becomes unbalanced and that person higher up on the see-saw may become a spoilt internet child.
Slash and burn,take away the enemies spoils of war.
These may sound like the words of a madman but you are being emotionally abused in the aggressive and passive senses,this person is controlling the relationship for their own benefit when they are active and then making you feel guilty by explaining their capricious absences as being down to crippling depression.
You have been left with no sense of self determination when it comes to dealing with her and you are also being saddled with the burden of an illness she won't even begin to talk with you about.
I have a relative like that,they only get in contact when they want you to hear all their bullshit then when you try to talk back they feign the need to vomit or tell you they have a migraine coming on.Then guess what they come back a few days later with a whinge about how unwell they've been and ,well you know ,you're going through the same thing right now.
It's an impossible tactical and strategic situation to deal with,you might as well throw all civility to the wind.
Being rude and obnoxious will not kill anything genuine in the relationship as it would have had to be there to be killed in the first place.