The text of the dialogue can provide indications of emotional context.
"Like we used to Mamma?" Hrafnhildur squeaked excitedly
"Einmitt, my little mouse, exactly", said her mother nostalgically
might be rendered as
"Really, Mamma? Just like we used to?"
"Einmitt, my dear little mouse, exactly like we used to."
or, if Hrafnhildur is normally somewhat excitable and her mother normally rather affectionate,
"Really, Mamma? Really? Just like we used to?"
"Einmitt, my dear little mouse, just like we used to."
(Repetition of another's phrasing is used in speech to seek clarity, express correction, and affirm emotional and intellectual understanding.)
or
"Einmitt, my dear little mouse, 'just like we used to'."
if the mother is more strongly affirming the certainty and Hrafnhildur's enthusiasm by explicitly quoting.
Some sense of nostalgia might be expressed in slipping into forms of speech of that previous time. Terms of address such as baby names can imply backward-looking affection. Vocabulary, grammar, and tone can be reminiscent of a previous time; use of words from a mostly abandoned mother tongue (as might be the case in the example text), speaking more or less formally than usual, and use of a poetic tone can imply nostalgia. While assumed context may be sufficient for the reader to notice and interpret such a deviation, such is easier to express when the setting and characters are more established.
For the alternative intent
"Like we used to Mamma?" Hrafnhildur intoned fearfully
"Einmitt, my little mouse, exactly", said her mother determinedly
might be rendered as
"Mamma ... do you mean like ... like we used to?"
"Einmitt, my brave little mouse, exactly like before."
As mentioned, context of setting and characterization can imply what characters are likely to be feeling.
Ever since the cat had forced them to move, their lives had been miserable. Hrafnhildur remembered how happy she and her mother had been.
...
"Really, Mamma? Just like we used to?"
"Einmitt, my dear little mouse, exactly like we used to."
or
The cat had forced them to move, but at least now they were relatively safe.
...
"Mamma ... do you mean like ... like we used to?"
"Einmitt, my brave little mouse, exactly like before we fled the cat."
The emotional context can also be expressed by unspoken thoughts and in describing accompanying actions.
"Really, Mamma? Just like we used to?" Hrafnhildur's eyes bulged with excitement.
Her mother's whiskers twitched at her own fond memories. "Einmitt, my dear little mouse, exactly like before."
or
"Really, Mamma? Just like we used to?" I can almost smell the cheese!
"Einmitt, my dear little mouse, exactly like before." Yes, barnið mitt, we can reclaim those happy days.
The alternate intent might be expressed
"Mamma ... do you mean like," Hrafnhildur shivered at the memory, "like we used to?"
"Einmitt, my brave little mouse." Her mother stared at her firmly. "Exactly like we used to."
or
"Mamma ... do you mean like," But we were almost eaten by the cat! "like we used to?"
"Einmitt, my brave little mouse." We have no other choice. "Exactly like we used to."
Attaching emotional context to ordinary speech indicators or using specialized speech verbs is not wrong and can provide an intermediate emotional separation compared to thoughts, which are necessarily intimate, or visible indications of emotion. Telling expression, such as "said determinedly", can also present a sense of hearsay compared to showing; while the writer usually wants the reader to accept the expression as simple truth, sometimes less reader confidence is desired.
Non-dialogue content can also act similar to punctuation.
"Einmitt, my brave little mouse. Exactly like we used to." We have no other choice.
is not exactly the same as
"Einmitt, my brave little mouse." We have no other choice. "Exactly like we used to."
or
"Einmitt, my brave little mouse, exactly like we used to." We have no other choice.
or
Dear heart. "Einmitt, my brave little mouse. Exactly like we used to." We have no other choice.
or
Her mother paused. "Einmitt, my brave little mouse. Exactly like we used to." We have no other choice.
Even purely environmental insertions can direct the reader's interpretation of emotion.
"Really, Mamma? Just like we used to?"
Scraps of paper rustled nearby.
"Einmitt, my dear little mouse, exactly like we used to."
The warm summer breeze pressed against them and then passed on.
is not a clear expression of excitement and pleasant reminiscence (and hope), but it may hint at such emotion.
Given that miscommunication of tone can occur between familiar friends talking in person, with all the nuances of voice and body language available, absolutely unambiguous communication in text should not be expected. Emotional ambiguity may even be useful, portraying hidden or suppressed emotions or a lack of emotional clarity in the character. Ambiguity can draw the reader to pay more attention ("was he being sarcastic?"), set up a later reveal (e.g., formal speech might indicate insecurity, authority, or precision of thought with the initial context implying a different interpretation than is understood from a more developed context), or allow the reader to imagine how the character feels based on the reader's conception of the character. Explicit declarations of feelings and motivations can even be discordant with the reader's conception, similar to the potential disappointment from an animated adaptation of a comic strip ("Dilbert doesn't sound like that") or a movie adaptation of a book ("Faramir does not look like that").