Sorry but I'm fairly new as well

so my advice is mainly guess work
I would say that, if you can, show her a great time. Take her out to do some new things and to some exciting places that she may not have been to before.
If it works she should really enjoy it, see you as different and more exciting, as well as associating those things with you. Things will be made better if this 'other' guy does nothing much with her or more likely does something generic with her...dinner, movie etc etc ZZZZzzzzz
Also, I know it's always said, be your self because you want a girl to like you for you don't you

BTW I'm not saying be 100% you

leave out the bad traits/habits and focus on promoting your best self.
I'm sure guys on this forum will have some more tips that you can select from.
Good luck man.