Thank you for your reply!
I have been working since last 2.5 years in the software industry, and directly applied to PhD programs after my bachelors. I think this was a huge mistake, I should've applied for MS programs to understand my research interests better, which is why I struggled a lot to choose between 3 good offers. You are right, I kind of forced myself into this offer considering a considerable amount of funding gap with other offers, a kind, young professor and a cohort of people from my country in the same lab, but the downsides are that she is the only professor working in something related to my interest. I already know that I will want to switch, but there is no one to switch to. After accepting I researched a bit and tried to learn about this domain and learn about future jobs more, but I seem to get more anxious that I am not liking the domain and future career prospects at all. I don't know if I should consider this getting cold feet or potential red flags.
From considering future careers, I think I will never be happy in a long term career in this field. But the funding concerns in corona situation is making me think if I should let go off a funded offer, or I should give it a try and then try to transfer. But I have came across posts regarding how hard a phd transfer can be and I am not sure if reapplying would be a better option. I have read a lot how unethical declining offer after April 15 is, and how burning bridges is very bad, and I am really concerned about it.
I have also received suggestions to defer and try in other places but that seemed to be unethical as well.