It will be ok. Phoenix had and was treated for a tick disease also (babesia). They are very treatable, especially when caught early. I freaked out also, but everything was fine after treatment.
You couldn't have known any earlier than now. If you're like me, you never even heard of tick disease before adopting greyhounds. The great thing is that you had Sadie tested and diagnosed. Now she can be treated and be well again. You did good