My BFF is giving me cold shoulder idk why?? 🙂

idk if I'm overthinking or not but my bestfriend has been really acting cold towards me for past few day's. It felt like she's kinda ignoring me when I call her she doesn't pick up and when I asked her why she wasn’t picking up my calls and she just said her phone was on silent but u can still she the missed call right? Idk this excuse felt lame to me and even on insta earlier we usually used to send each other reels literally everyday but now she suddenly stopped and now she just leaves them on seen. She never did that before and I even notice she hide her insta story from me which honestly makes me feel worse and our boards exams are going one rn so I thought maybe she's just stressed or something but yesterday after exam at the centre I asked how it went and she just said it went fine and she asked me I said mine was good too I only left 5 marks but idk why but I kind off felt like she wasn't happy hearing that . and on the way home she barely talked earlier she used to talk alot and we'd yapp all the way to home. Maybe I'm just overthinking but this behavior is really hurting me alot. I'm pretty introvert and she is basically my only friend for last 5 years and I've become kinda dependant on her. I really don't want to lose her she's literally my only friend :-). Idk if I should ask her directly if something's wrong or just give her space