I'm so sorry you're going through this.

The only suggestion I can offer is to explain to your friend, in person now, how you're feeling and how hard it is to put a friendly mask on (which must be exhausting, amongst other things) when around other people. Hopefully she will understand, and you will feel a bit of the load lifted from your shoulders. It's truly awful how you're feeling, but it must be even worse being alone with it.