You're correct in theory, but "por" does not mean "towards", and "por" was the word they gave us.
I think, as we get farther along, Duo gives us tougher sentence structure, so we can learn to think in Spanish (rather than thinking in English and translating into Spanish which takes a lot longer.) I know I when I'm describing something in Spanish, I actually think "the house red" or "the shirt blue" to help me remember to put the adjective after the noun.
It is quite possible that in Spanish, there is no such phrase as "What do you feel towards her?" or. "What do you think about him?" Perhaps, "for" is the only acceptable translation. If so, Duo MUST insist we say it the way Spanish speakers would understand it. It's frustrating to be marked wrong without knowing why. However, I would be even more frustrated if I asked a new big brother or sister "Qué siente hacia (toward) su bebé", and they laughed me out of the NICU. The way one five-year-old brother did when I told mom she could bring "camisetas y sombreros" for the baby. (Apparently, sombrero only refers to those hats with the large oversized brims, not baby hats. :-)
"Se" means, grammatically, there is no one doing or causing the action. So it can never be grammatically correct to say something like "Los huevos se cocinaron por el cocinero". Nor "Él se mató por el asesinato". If you want that kind of sentence construction it would either have to be "Los huevos fueron cocinados por el cocinero" and "Él fue matado por el asesinato", or Los huevos se cocinaron" and Él se mató". I do not know why.
Sentir and sentirse are both valid verbs, the second being the reflexive form-- as in how you feel (to yourself.) We still need to "feel" (perceive, sense-- i.e. sentir) other things or feel about other things/people ("percibir por los sentidos.") If the 'se' was used in a sentence (not this one) it would refer back to "her"-- or yourself if 'me' was used instead of 'se'.)
Por ejemplo, usando el reflexivo: No me siento cómodo en lugares donde hay mucha gente.
In this Duolingo example, it's not about how she feels to herself or about herself, but about someone else (her husband.)
At least, that's as clearly as I can explain it, from a non-native POV.
I thought "sentir" was meant to "feel something" as in an object ( she feels the sand beneath her feet" but "sentirese" was meant to "feel some emotion/etc" ( she feels sad - ella se siente triste) so I thought this sentence ( feeling something for her husband) was sentirse but it's not that simple?? Thanks.