I believe it would probably only take one correction for people to get right, but especially due to the familiarity of [name_m]Timothy[/name_m], [name_f]Timothea[/name_f] is not at all likely to get your preferred pronunciation on the first try really ever.
It’s a pretty name and your choice in pronunciation is lovely! In the US, I just don’t think it’s intuitive enough to be a standard pronunciation. You’d just need to be prepared for lots of correcting in day to day situations where people may not already know little [name_f]Timothea[/name_f].