She did become stronger by mastering Haki before half of the Straw Hats. She went up in ranks, and mastered a power only known to Vice Admirals. Monet was strong enough to slow down Luffy, and she was one of the highest ranking officers of Doflamingo. I think it would not make any sense to keep Tashigi weak when we are reaching the finale, and it would go against the message of the series of improving, and becoming better.
@KiriNigiri
I think power is essential in the One Piece verse as well in the real world. Tashigi wants to challenge Zoro because deep down she admires his strength, and courage. No one respects a weak person. There is a reason why people have endless discussions who is the strongest character in the series. Oda set up specific ranking systems for pirates, and marines. In real life, we also have endless debates about who is the best athlete, who is the Goat, who is the most beautiful woman, who is the most handsome man, the best films, the most powerful country, and so on. Life is nonstop competition. The reason why there are fans not shipping Zoro and Tashigi is because they deem she is not good or strong enough. Imho, this is the last opportunity for her to shine and shut up her haters once and for all. I think it all depends on how Oda chooses to solve the Kuina and Tashigi connection.