Might be a little heavy- Would “I miss you” be inappropriate in this situation?

In December and January, my grandmother (91) suffered a fall, congestive heart failure, and a massive stroke. Not all at once– the heart failure was in late December, the fall was like a week later, and the stroke must’ve been like no less than 2 weeks after that. She’s currently in in-home hospice care out in Los Angeles with my uncle, because she visits him during the winter and returns to Delaware in the spring. For the record, I’m in Pennsylvania. So I can’t exactly see her. She’s lost most motor ability and can barely speak. It was very frightening and shocking to hear for the first time. Given how She’s sleeping more and eating less, I’m guessing that time is running out.

Today is her birthday. Of course, my phone service is out at the moment. The signal is bad in this area. So I asked my uncle to tell her I said hello and happy birthday. Also that I love her. But I kind of refrained from there because I can’t tell if “I miss you” is OK to say here. We all know, including her, that she won’t be returning to Delaware. Effectively, thanksgiving was absolutely the last time we will see each other. And I’m really thankful I went despite my mental health. Got to hug her and all. But that’s the thing: I will not see her in person again until… Well. You know. So is it OK to say “I miss you” when I know and she knows that was the last time?