Highlighted weapons are free options.
Mona can use her Burst to apply the Omen debuff on enemies and allow teammates to deal more damage. This is most commonly seen in Freeze teams. Mona's main role on a Freeze team is to provide Omen debuff from her Burst as it is extendable via Freeze mechanics.
Note that you must apply Cryo before casting Mona's Burst for the extension to happen. Omen Freeze extension can be done by reapplying Cryo and Hydro aura consistently (this can be done with Cryo / Hydro infused Venti Burst + on-field Cryo / Hydro aura).
Mona's Burst applies bubble and Omen debuff upon cast, the count down timer only begins when the bubble is broken.
Frozen enemies can have their bubbles preserved as long as enemies stay in a frozen state. This technique makes Mona a priority Support for Cryo DPS teams.
Offensive stats aren't actually needed on a Freeze Support Mona, focus on the artifact set bonus and stack Energy Recharge for comfortable Burst uptime