Covid question..

So my girlfriend's best friend has had covid for 3 weeks. Who knows if she's cleared or not. That's just since she was diagnosed. Anyways, I stay with my girlfriend sometimes but I also live with my elderly grandma primarily. Anyways tomorrow is the 3 week mark. I'm actually scared for my gf to see her bc what if I get it and take it home to my grandma? I know she wants to see her friend so I wouldn't stop that, it's going to make me stay away from my girl for a few weeks and she's mad bc she can't kiss me on new years eve. Which isn't my fault since she's choosing to see her friend who has or had covid. I have to be careful bc of my grandma. She's diabetic and has heart problems. I'm not going to fully disclose her info but she struggles with her health. So do you think I'm overreacting for not wanting to see her for a few weeks after she sees her ex covid friend? I mean this girl hasn't even been cleared by the doctor on a follow up test. What should I do?