How do I tell her I tested positive for an Sti?

So I had a hookup with a new girl I’ve been seeing about a month ago (Unprotected. Stupid, I know) and I went to get tested Friday. The results came back positive for trichomoniasis. I started my 7 day treatment today. Both my ex gf and I tested negative during my last relationship and were both faithful to each other. My ex and I have hooked up a few times (we both didn’t hook up with anyone else).

I haven’t done anything with my ex since I hooked up with the new girl just incase some shit came up and I didn’t want her to be in the mix of a dumb decision. I told the new girl I was clear and I have evidence in my records. I’m scared that she won’t take that shit lightly and think that I was lying and gave it to her or some shit. At the same time, she has a huge crush on me and maybe I’m just overthinking. I want to tell her in person ASAP. Our work schedules are opposite today but we’re both off tomorrow. I don’t want to wait till tomorrow and I don’t even know if she’s available tomorrow either but at the same time I don’t want to tell her over text cause I don’t want to risk something being screenshotted. I also don’t like discussing things like this over the phone either. How should I bring this up peacefully without causing conflict? Kinda panicking right now