You are 22 years old and your question is too elementary. The replies are given already I hope you understand the issue.
Having a family planning operation means she wont get pregnant thats all. The other aspects on these types of relationship are still there. Before you she had three fuck buddy like you, how are yo so sure you are the only one she is sleeping with right now? She might hace other male friends or husbands too. Assuming none of these three guys had any STI/STD, she still can pass that to you with her other fuck buddies.
Add to the risk of STDs, there is always a chance of being blackmailed too. Not with pregnancy still if she complains about forced sex of rape, law is always favoured towards women. If she is married, getting in legal issue of adultery is there too. And finally if she breaks out the news to others, you may lose your future girl friend, but your family may lose the name.
Want to take so many risk? Better get a girlfriend of your age where there is a future, and drag the relationship forward, with or without sex. Anyone who has some ecperience on free sex in life always know, its not always free, sometimes its too costly.