My first guess was St. Faustina Kowalska because of the rays of mercy from the heart of Jesus (compare here), but that it's coming from a crucifix (and not an apparition) makes that a little less likely, along with the saint's pose and that she's about to be crowned by cherubs.

St. Teresa of Avila has a similar kneeling-before-a-crucifix look sometimes, but that's of her vision of the dove of the Holy Spirit, so kind of different also.

I don't see any St. Clare of Assisi images that look like this.

It's hard to search for similar images based on this description, though, because all the terms I can think of are pretty generic in religious art.