Faking a mental illness...

I have a friend who used to be alright and had a great personality, but in one day she changed for some reason, she started telling me she had depression and social anxiety even though she hadn’t been to a hospital to get diagnosed.
I love her so much but I’m just sick of feeling like she’s faking it, during recess two weeks ago on a Tuesday, she was all cool and stuff and the next day she just started getting clingy whenever we’re around a bunch of people, and I’m pretty sure anyone can tell if someone is actually shaking or faking it, to me it seemed so fake, one day she’s alright then the next moment she starts crying and when she gets the attention of the entire class she stops. And whenever she’s upset everyone is relying on me to “make her happier” just because I’m her friend, her happiness doesn’t rely on me.
I really don’t want to sound rude but I feel like she’s faking it 100%. You can’t just get anxiety in one day.
Thank you for reading.