Be safe Kati. Please don't harm. Seek help if you need to.
... think it's pointless because she haven't really helped my friend. I know everybody is different but still. I'm so confused, what should I do???
Because I really wanna know is my happy-depressed-happy mood just a temporary thing or is it something serious like bipolar disorder or I'm just thinking that I have mood swings
To expect different you need to do different. If you've never seen her, give it a go. Don't let your friends opinion cloud your own.
Without knowing your exact situation, I still believe you have nothing to lose by trying this therapist out. If it doesn't work, you move on to another one. You and your friend are likely dealing with different problems, so go ahead and try.