Answer: My internet connection is not good enough.
Step-by-step explanation: This one may be pretty commonly used but also a common problem people always have and it's pretty unavoidable. Tell her that the call\meeting gets super laggy and then ends up freezing and that doing it over voice is a better option for you so you can get the best learning experience or something like that. Basically pretend you care until he\she believes it.
Good luck <3 Let me know if you need another!