There are some dialog plugins in marketplace. I would obviously recommend my own, Snowfall Plugin, it has the functionality you’re requiring.
If you don’t want to purchase a plugin, you can do it yourself by doing a “find and replace” search in your dialog String, replacing “[npc.name]” to “Jessica” every time a dialog is going to be show in a Text widget. You can do that with the Replace Blueprint node.
The most basic functionality can be achieved with the Format Text node. Check here for a brief example.
For something more in-depth do consider giving Rich Text Block a go. It is substantially more powerful and flexible but does require more upfront work to set it up.