I don't agree with Gamoras plight in the movie as being there "just to provide motivation for a male character". She isn't captured and eventually killed so that Star-Lord and the Guardians have motivation to go after Thanos. They already have that motivation, as finding and killing Thanos is the entire purpose of Drax's existence at that point, and they had already picked up Thor, who provides them with additional incentive to track down the Mad Titan. I do agree that she is killed off to show that Thanos is capable of love and regret, but I don't think that is what the "women in refrigerators" trope references. Gamora was already established as a strong female character, possibly the most feared assassin in the galaxy, more than able to hold her own against the various threats the Guardians have faced, not to mention against the Guardians themselves. Her identity was never tied to the love interest with Star-Lord, so I don't think she fits the trope.
When it comes to showing Thanos' ability to love, there were few options available. In the comics, they show it through his love for Lady Death, but to do that in the movies, they have to introduce another major character with all her attendants in a movie that is already overloaded with major characters. Once you step back from going that route, you have to look at what has already been established for the Thanos in the MCU. He has two adopted daughters, Gamora and Nebula, and he clearly favors Gamora, so if he needs to make a sacrifice to show he is capable of love, killing Gamora is the most relatable way to do that. It also gives a big kick in the gut to the audience, because her character is so well liked. Much of that has to do with the strong female character she represents. It is probably the most emotional scene in the entire movie, none of the other deaths play out with the same emotional depth, and most happen so quickly, one after the other, that you don't have time to pine for the loss of those characters. If any scene in the movie is going to cause tears from the audience, this is the one, and that is why it is there.
Honestly, when I first saw the "women in refrigerators" link, I thought you were going to mention Nebula in connection with it, as she is captured and tortured by Thanos in order to obtain information from Gamora. Except for Gamora being her adopted sister, rather than a male love interest, I think that part of the movie fits the bill a bit closer, even though it is an homage to the torture of Nebula at the hands of Thanos in the Infinity Gauntlet comics. And, if you know how that ended in the comics, what happened with Nebula in that case does not fit the trope either.
You can also point to the flipping of this trope in the movie, or at least a very similar trope (damsel in distress), where Vision's plight provides motivation for Scarlet Witch. He becomes the damsel in distress, and a Scarlet Witch tries to be his white knight.