AWKWARD ZOMBIE

You say it is bizarre for Samus Aran just to freeze up like she did in Other M against Ridley, but she has done this to an extent in every Ridley encounter of the series (excluding Super Metroid since it lacked cutscenes).

I'll start with Metroid Zero Mission, the remake of the original Metroid. This is Samus' first encounter with Ridley in the series. When she is about to exit the room where Ridley is marked to be fought on the map, a short cutscene is shown. In this cutscene, Samus can be seen appearing shocked by Ridley's sudden appearence and looks angry as he is seen swooping towards her via the image on her visor. Despite being angry though, she still becomes frozen enough for Ridley to take advantage and gain a first attack on her with his fire breath attack.

Metroid Zero Mission - Ridley encounter cutscene
http://www.youtube.com/watch?v=k-smcuIzuxw

Now, Metroid Prime has Samus encountering Meta-Ridley three times based on appearences. The first is in the Frigate Orpheon, and what does Samus do as she watches the menace free itself? She just stands there, and one could say that this freeze on her part led her to ultimately lose track of Meta-Ridley (since he had a head start on her). The second appearence Meta-Ridley has is in Phendrana Drifts, and again Samus is frozen still as Meta-Ridley flies over. The final appearence is the actual boss encounter at the Artifact Temple, and before players can control Samus there is yet another cutscene. What does Samus do? She basically stands in place, and only ducks slightly to avoid Meta-Ridley's bombing attack.

Metroid Prime - Meta-Ridley encounter at the Artifact Temple
http://www.youtube.com/watch?v=F0FGIl4zPqY

She does aim her arm cannon up at him, but doesn't shoot, and even puts it down when he flies back up again. On his second fly over of the Temple, he sends out bombs directly at Samus who is frozen to the spot she's at. Sure, she ducked and moved her arm to try and shield herself, but she still gets hurt as she makes that grunt noise. If Samus isn't frozen up by his appearence then she should have made an effort to effective dodge his bomb attack. That doesn't happen though.

Metroid Prime 3 is the best example of how frozen Samus becomes when faced with Ridley. In the cutscene, she's in Generator C and rolls out on a ledge. Then there's Ridley rushing down towards her. What does Samus do? She stands there and shoots upwards at him. Shooting upwards wouldn't be so bad if she tried to actually fire off shots that would have a chance against Meta-Ridley, like a Charge Shot. While she is firing at Meta-Ridley, she is frozen in place and allows herself to be taken down into the massive shaft of the Generator and through a sheet of glass along the way. In the end, if Rundas was not there, Samus had a high probability of dying in the Generator due to the fact she was unable to move to dodge Meta-Ridley when he dived at her.

Metroid Prime 3 - Generator C Meta-Ridley encounter
http://www.youtube.com/watch?v=9hHBfStwJEs

I know it was not mentioned by sirboulevard, but the Omega Ridley encounter does show signs of a similar weakness in Samus Aran.

Metroid Prime 3 - Omega Ridley encounter
http://www.youtube.com/watch?v=TRX_WY4ey6s

I will start off by saying Samus' reactions are a bit better in the cutscene, but not by much. As soon as Omega Ridley comes into the main chamber of the Leviathan, and as he flies about, Samus can be seen glued to her position. She does move to dodge Omega Ridley's dive bomb attack. As the creature moves towards Samus, she just slowly backs away. No arm cannon pointing at him yet despite how close he is to her. She has a good reaction to his fire breath attack, then finally points her arm cannon at Omega Ridley. Better reaction overall, as I said, but there are points in the scene that show her being frozen and not taking action.

There you have it, Samus shows similar showings of the same fear and freeze up she has in Other M in all Metroid games that have cutscenes with Ridley. It's really not new in Other M, just more fleshed out.