"I'm not good at orienting" isn't natural. I think you mean "I'm not good at giving directions". There is a sport called 'orienteering" and for this you can say, "I'm not good at orienteering". Your 2nd sentence is ok. It is better to replace 'in' with 'for' and say, "If either of us are absent FOR the meeting, it wouldn't be good." The 3rd sentence is ok, but very casual. Better to say, "She's ill, but she refuses to let me take her to the hospital."

Hi Pelin! I'm not good at orienting. If either of us are absent in the meeting, it wouldn't be good. She's ill, but she refuses me to take her to the hospital. *** You may say something like this: At work, I am not good at orienting staff. If either of us is absent in the meeting, it wouldn’t be good. I worry because my colleague is ill but she refuses me to take her to the hospital. (This last sentence can be more specific to who is ill and what is the relation to your first 2 sentences) Have a great day!!

The first, not sure what you mean by orienting? Maybe: I'm not good at directions (if you are speaking of finding your way around a location). Or: I'm not good at providing direction (if related to work and training someone). Second sentence is fine. Third should be: She's ill, but she refuses to let me take her to the hospital.