If her magic depends on the presence of those mana-based beings and she isn't bringing one of them with her, then you're correct that she wouldn't initially be able to access her magic, but if you wanted her to regain one of those beings later in game it would allow her to access mana again (assuming that these beings are not themselves appable creatures). Alternatively, she could regain working blastia, if you prefer that option. It's possible to regain items even if they have been destroyed or modified in canon at a character's canon point.