If the speaker is a woman, shouldn't there be an "e" added to "senti"?
There are two types of exceptions I know of to past participle agreement with pronominal verbs.
a. If the verb takes an indirect object.
Elles se sont vues. (direct, agreement)
Elles se sont parlé. (indirect, no agreement)
b. If the direct object comes after the verb.
Elles se sont lavées. (agreement because "se" is the preceding direct object)
Elles se sont lavé les mains. (no agreement because "les mains" comes after the verb).
This sentence doesn't fall under either of those categories.
I'm not sure Duo is being as clever as you’re suggesting - they don’t always have the gender of the speaker and the text in accordance: this may just be an example. In the second half of the tree, I’m also finding the word tile sentences have alternating male and female voices for successive words, which sounds even weirder..