I should be thankful that I could see her for at least 15 minutes rather than not being able to see her at all.
この場合、次のような言い方ができますよ。
ーI should be thankful that I could see her for at least 15 minutes rather than not being able to see her at all.
「全然会えないより、15分でも会えるのだから感謝するべきだよね」
ーI'm glad I could visit with her for at least 15 minutes. It's better than not being able to see her at all.
「15分でも面会できるので嬉しい。全然会えないよりましだから」
ご参考まで！
カナダ 
