Since you appear to want something more with this work crush and she tends to avoid you when you go to lunch break, it may be best to get closer to her work friends and give them an opportunity to get to know you.
This may lead to them inviting you to engage with them on breaks and she will be with them in some of those moments.
These moments will give you a better opportunity to provide her with a substantive impression of what your personality is like as you talk to her work friends.
This impression may cause her to start feeling less stressed whenever you are around and this could lead to the both of you beginning to have pleasant short greetings or conversations when you see each other one on one.
From here, you may be able to build enough rapport with her that she starts considering the possibility of giving a workplace romance a chance.