how to say NO to a senior colleague?

Kim • engrkikay ❤️

I am having a hard time saying no to this senior colleague whenever she ask for favors and whenever I am the one asking for favor, she would turn me down and talks negatively of how she's not getting paid so why would she do it. How will i turn her down without losing my image as a newbie in the company? She's been in the company for 30yrs and i will turn 2yrs nxt month.