I'm a bisexual girl, at the moment I'm in love with this straight girl and I don't know what to do!
I like her too much and I would not want to lose her in case I told her what I feel for her.
What should I do?

Before we go in to further details, is this girl a close friend of yours or somebody else that you don't know?
if she's a close friend of yours, she may understand the situation if you talk it good to her.

She's a dear friend of mine, a volleyball friend

I see, well, i don't know what others would think. but i think you maybe should talk it out slowly with your friend, like you love her and she's like your eternal soulmate.
besides love isn't always about sex, it's about how you want to be your loved one everytime and spends your time them.
if she's also think you as her dear friend, she probably wouldn't get away from you. just as i said, talk it out slowly, don't rush, take things one step at time, it does takes process to get there.

Thank you Kohseider!