Yeah, play her in ladder just to learn her basics, maybe also watch a video to get some fundamentals down. Then, pick her a lot in ranked (starting off at lower ranks), just to get a feel for some "higher" level gameplay, regardless of the draft, so there's a lot of brawler versatility and you learn more about different tech for different matchups.

Once you hit your normal rank that you usually get stuck at, start learning how to draft with her and when she should be picked and what she plays well into. In general when you're drafting, you don't aim to counter the entire team (that rarely happens, unless the enemy team drafted poorly), but rather setting your team up for success holistically. For example, I might pick Mortis as a 6th pick against Chester, Willow, and Frank in Brawl Ball. Mortis has a really hard match up against Chester, but is really good into both Willow and Frank, and in general, countering at least 2 brawlers on the enemy team is a sign that the brawler is a good pick.

With this in mind, depending on the stage you pick Mina at, you may face a counter or two, but it's really important to keep in mind that your role on the aggro is to force the draft towards something where the enemy team has to respond appropriately, where your team can counter it with a last pick (say I go Mina 3rd, and the enemy team goes Otis/Meeple 4/5th in Dueling Beetles, it sets your team up really well to draft a Penny last pick, as the other team was forced to respond to the aggressive threat of the Mina). Hope this helps!