I have some monsters that I can use, but put specific monsters aside (to focus on the strategy), what strategies are worth to try on her?
PS: Assuming a 6* with high HP pool.
There can be 3 ways to counter Rina :
Monsters who doesn't need high crit rate and can give high dps. Ramagos is counted here and his 3rd can almost 1-shot a Rina albeit slow and takes time.
Using debuffs to prevent/remove her shield. Megan and Belladeon are examples. Inflicting continuous damage can also be useful, so Orochi is counted.
Very high dps (ignore defense if possible). Rina/Neal with Katarina if it's like 1-2 Rina, Sieq with Lushen if there are 3-4 Rina. Better if have AoE defense debuff on team (like Malaka's 3rd skill).
Rina's shield is a passive. So using Tesarion's(Fire Ifrit) ancient power passive that causes oblivion (debuff that prevents passives from activating) is the easiest way to deal with rina. (and fuco) After oblivion is applied you can kill Rina with anything, crit all you want, her shield wont activate.
You can as well counter her with Chiwu (removes Buffs and applies a buff blocking debuff)
...or with DoTs (Orochi, Baretta or even Veromos work here). Violent runes help a lot when going for DoTs.
In guild wars, usually a Veromos alone works, if you just spam the first skill. 4 DoTs remove a full shield (4 * 5% = 20% = it's depleted) and the next attacker can go full force on her.
One way I counter Rina is with Chilling (water Jack o lantern). He steals her passive shield, and let's the last two hits land. Its time consuming, but works.
Speed team
andClhoe (immunity team)