To make your girlfriend angry, you first need to understand why she is angry. Sometimes, your girlfriend may get angry over something small, such as when you forgot an important anniversary or if you made her feel hurt by something you said unintentionally. Whatever the reason, the first thing to do is to admit the mistake and apologize. You can choose to apologize directly to her honestly, or show your apologies by giving a gift, arranging a romantic surprise, etc.
After apologizing, you need to give your girlfriend enough security to let her know that you care about her and are willing to listen to her feelings. During this process, you need to be patient and not try to interrupt her or solve the problem quickly. Instead, you should listen carefully to her complaints and grievances and respond positively, such as "I understand your feelings" or "I understand your point of view."
After your girlfriend has expressed her feelings, you need to come up with a solution and commit to improvement. If you are able to find a mutually acceptable solution, then your girlfriend is likely to lose her temper and regain trust in you. For example, if your girlfriend is angry that you forgot an important anniversary, you can promise to pay more attention to these details later and make up for her disappointment with a special gift.
Finally, you need to give your girlfriend enough attention and pampering to let her know that you care about her feelings and needs. You can show your love through daily care and greetings, giving her affirmation and encouragement often, spending quality time together, etc. This can make your girlfriend feel your sincerity and change, and gradually discourage and reconcile with you.