x3!
never be the 3rd party in a relationship.. cos u wun want to have a
3rd party in ur own relationship too..
jus stay as frns to her.. dun be the one who cause the breakup of
her relationship.. but if she do really breakup wif her bf, then go
for it! 
meanwhile, leave the option opened to know more gals too.. who
knows you might came across someone else... 