Olwen looks sympathetic, since Reiner seems so desperate but has to reply that there is currently no possible way to bring anyone specific to this world - nor is there a way to "exchange places". That is an unfortunate nature of the magic: you can't pick and choose people. Otherwise everyone here would be willing helpers.

He, however, promises Reiner that if they manage to find a system where they can summon people, Reiner would be one of the first ones to know. They are constantly studying the summoning magic in hopes of improving their methods.

If Reiner is willing, Olwen offers to listen to Reiner's story and why this person is important to him, but at the same time he won't push for answers. He's merely offering a listening ear.