Ying is limited to 2 stationary Illusions. If Ying wants to push up she needs to sacrifice illusions to make new ones to heal or her team will need to fall back for healing. Killing her or her Illusions gives no healing for the enemies to retreat to.
If you can see and kill Ying, Prioritize her over her Illusions. Killing Ying makes her Illusions despawn and prevents her from Healing/Shattering. If you can't see Ying and have no/low cauterize killing Illusions might stop healing from her.
Something you should always do is focus fire. If Ying has the Life Like Legendary Card, this is even more effective as the heal beam loses 30% of its healing ability, but if you spread out the damage, she will have 40% extra overall due to 2 beams.
Your ult is extremely important. you need to do dmg to get it quickly. moral boost and generalized vollys of weapon dmg into the frontline when not in active combat should bring your ult to use very quickly
Find where her illusions are and use that to your advantage. If someone targets her, she will likely try to teleport away and confuse you. Surprise her by having someone else near her spot or quickly running after her while staying away from enemies