Be cautious but firm. I say “cautious” because mawile are generally known for their deceptive abilities, and that extends to more than just in battle. If a mawile has their heart set on something, they will often use their cuteness and deceptive natures to trick those around them into getting it. Always be on your guard around a young mawile, as the species is particularly cute when recently hatched and intelligent enough to know that.
That having been said, set boundaries for your mawile. Establish the fact that she cannot battle in full-scale matches involving experienced pokémon and be absolutely firm in telling her this. Never take her to a battlefield, but if avoiding one is difficult for you (as battlefields are common in public spaces, such as parks and pokémon centers), refuse to battle with her and make it clear to trainers who might approach that you’re not interested just yet. This may force you to cut back on training with your other pokémon, but until your mawile is old enough, it may be for the best.
However, you don’t necessarily have to forgo training routines altogether. Instead of engaging in hard battles, consider using your other pokémon to set up play matches with your mawile. In other words, allow your mawile to “battle” your other pokémon while making it clear to your team that they’re to go easy on her. Roughhousing, as odd as this may seem, is a great way to encourage your mawile to bond with the rest of your team while gaining the strength and experience she needs to grow. Likewise, it’s an excellent way to teach the rest of your team to control their abilities (as it’s easier to go all-out in a match but takes far more discipline and strength to hold back). This may be a perfect compromise for an insistent mawile who’s far too young for actual battling.
Of course, if she shows no interest whatsoever in battling, then that’s an entirely different matter, and for that reason, I would suggest worrying less about whether or not she will be insistent on battling. Some mawile are quite enthusiastic about the prospect, but others may need time to warm up to the idea of battling at all. It all depends on the personality of your hatchling, and you really have just as much of a chance to handle a disinterested mawile as you are one that wishes to fight as soon as possible.
Good luck, anonymous, and congratulations on the newest addition to your team!