Is it okay to have feelings for someone else’s girlfriend?

I am a 35 y.o. male metalhead seeking for a metalhead girlfriend. My relationships in the past did not last long because of compatibility issues(no common interests) . A few months ago, I added a female guitarist on Facebook(I also play the guitar by the way) and I found out we share some common interests in bands like Metallica, Slayer, Black Sabbath,e.t.c. When I posted something related to music on my wall, she sometimes reacts it well by either liking it or giving a reaction and commenting on it. I did the same to her posts too. I also chatted with her on Messenger whenever she posted something on her Stories and we had a good conversation. The only problem now is she has a boyfriend who is also a metalhead and I wish I could have met her earlier . I have some feelings towards her but I just can't simply state my feelings through Messenger because of obvious reasons. Now with the lockdown situation in my country, it is difficult for me to go meet people at pubs because they are closed and my only hope is to see her performing live once the lockdown is lifted up. So, is it okay to have feelings for someone else's girlfriend? I don't want to rush to be in a relationship and please do not suggest me online dating because it did not work for me .Thank you!