The real red flag for me here is the emotional manipulation: "If you really loved me, you would marry me" and the pressure after only one month of dating. Also the pressure to have sex.

After I told her why I didn't want to do that she threatened to leave my apartment

Stay away from this type of person whether they need a greencard or not!

The question was

"How can I find out if my gf only wants me for a green card."

The answer is, you can't really, and probably it is not a flat yes or no. So, yes, she might need you for the green card but she might actually like you.

But, what was described above is enough to end the "relationship" because there are several behavioural patterns:

• emotional manipulation
• pressure to have sex
• pressure to get married
• most likely dishonesty
• the drama: after the OP's refusal to have sex because he did not want to get her pregnant, she "threatened" to leave the apartment she was so upset he had to "calm her down"

After I told her why I didn't want to do that she threatened to leave my apartment, but I eventually calmed her down.

• the OP does not trust her. This might be justified because he has a good gut feeling about people. But it does not really matter. He does not trust her. Exhibit a: searching for a hole in the condom. Exhibit b: asking this question here.

I thoroughly checked for anything that looked like a hole in the condom. No hole was found.

• she appears to get angry for no reason. Being disappointed because he did not offer to marry her might be appropriate. Being angry after one month and after a night he staid up late to help with job applications seems very inappropriate to me

Also, this would probably be more obvious if the gender was reversed.

Disclaimer: I live in Germany. Culture is reasonably similar to U.S.

The real red flag for me here is the emotional manipulation: "If you really loved me, you would marry me" and the pressure after only one month of dating. Also the pressure to have sex.

After I told her why I didn't want to do that she threatened to leave my apartment

Stay away from this type of person whether they need a greencard or not!

The question was

"How can I find out if my gf only wants me for a green card."

The answer is, you can't really, and probably it is not a flat yes or no. So, yes, she might need you for the green card but she might actually like you.

But, what was described above is enough to end the "relationship" because there are several behavioural patterns:

• emotional manipulation
• pressure to have sex
• pressure to get married
• most likely dishonesty
• the drama: after the OP's refusal to have sex because he did not want to get her pregnant, she "threatened" to leave the apartment she was so upset he had to "calm her down"

After I told her why I didn't want to do that she threatened to leave my apartment, but I eventually calmed her down.

• the OP does not trust her. This might be justified because he has a good gut feeling about people. But it does not really matter. He does not trust her. Exhibit a: searching for a hole in the condom. Exhibit b: asking this question here.

I thoroughly checked for anything that looked like a hole in the condom. No hole was found.

• she appears to get angry for no reason. Being disappointed because he did not offer to marry her might be appropriate. Being angry after one month and after a night he staid up late to help with job applications seems very inappropriate to me

Also, this would probably be more obvious if the gender was reversed.

Disclaimer: I live in Germany. Culture is reasonably similar to U.S.

Some resources on "red flags" / emotional manipulation:

• https://www.goodtherapy.org/blog/red-flags-are-you-being-emotionally-manipulated-0917197
• https://www.thehealthy.com/family/relationships/emotional-manipulation/
• Harvard Business Review: "Are You Being Influenced or Manipulated? Learn what signs to look out for" by Ruchi Sinha" (for the business world, but a good read nonetheless): https://hbr.org/2022/01/are-you-being-influenced-or-manipulated