Why is a co-wife called a Tzarah?
Radak: Usually, co-wives are enemies.
Why does it say "Gam Ka'as"?
Rashi: This is anger after anger. She did so constantly. She would say, did you buy a scarf for your big son, or a cloak for your small son?
Malbim: She had anger due to Peninah, and her own anger, for being barren.
What is the meaning of "Ba'avur Har'imah"?
Rashi citing Bava Basra 16a: She intended l'Shem Shamayim; she pained her in order that she will pray for children.
Radak: Har'imah is like "Ra'amu Panim" (Yechezkel 27:35; anger).
Radak citing Targum Yonasan: It was so Chanah will envy Peninah.
Malbim: Har'imah is Makor (like a gerund) based on the Hifil; she was always angry and complaining.
Why is there a Dagesh in the Reish in "Har'imah"?
Radak: It is to strengthen the pronunciation of the Reish. The same applies to the Kuf in "v'Nesakenuhu Min ha'Ir" (Shoftim 20:32) and other places, to beauty the pnun.