Article in English: She should know that she can count on you through thick and thin. You'll offer her a shoulder to cry on when her relationships go wrong. You'll drive her to the station in the middle of the night to get back to her family in the pouring rain.  That you'll study with her for a really hard test. This doesn't have to be said -- after enough time, it'll be understood. Girls get emotional. When she gets like this, it's important just to listen. She may not want an actual solution, regardless of how much she's complaining. Being there, listening to her, and telling her she can handle whatever she's going through is infinitely valuable on its own. If they want to date her, it's fine by you but you're always keeping an eye out for her. That'll keep them on the straight and narrow too. And that's what being a true friend is all about. After all, she's like your sister, but better (no fighting over the bathroom). Let your girlfriend know she's your friend, period, too! Sometimes girls get a bit intimidated by other girls; if you approach this topic like it's no big deal, your lady should (hopefully) not have a problem. Heck, maybe the two of them will even hit it off! There's a school of thought that says guys and girls won't always be "just friends." At one point in time or another, either she'll have feelings for you or you'll have feelings for her. If this does happen (which it might), stay open about it. The absolute worst is living in a does-she-or-doesn't-she state of mind. Avoid this by being direct. And because you're such good friends, you can do this! Hopefully she'll be direct with you, too. If you start to notice mixed signals and you think she might be developing feelings, let her know how much you appreciate her friendship. There are delicate ways you can tell her you're just friends without hurting her feelings. Nip the problem in the bud as soon as you can!

Summary in Indonesian:
Dampingilah ia. Biarkan teman Anda yang lain mengetahui bahwa ia teman Anda, titik. Bersikap terbukalah mengenai perasaan Anda.