I know a lot of middle-aged Hispanic Yolandas (all use the full Yolanda, no nickname,) so it doesn't seem odd or awkward to me.
The thing about this case is that there really isn't anything wrong with Yolanda- it's a fine name, if a little dated. It made the top 100 for a few years in the 60s and 70s, so there are plenty out there and they really aren't that old. It's not like Pixie, which can have some seriously negative connotations, it's just not your taste in name. It sounds awkward to you, but I don't expect it would hold someone back in the workplace.
Yolanda is a bit dated but it's also very charming. It reminds me of the character that Christina Hendricks played in Firefly (it was one of he aliases incl Bridget and Saffron). Sightly geeky but very pop-cultural reference there with a very sexy embodiment. (nn Yola could be great and in line with the whole modern yolo idea without being too on the nose for a nn).
I grew up bi-cultural and actually find it very odd that people give themselves "English", "Spanish", etc. I get the idea of "fitting in" but I can't see someone being less likey to hire someone for having a traditional Chinese name spelled out in a Latin based alphabet. If anything I'd encourage my students to choose "English" nn's that sound similar to their actual names if those are difficult for the average westerner to pronounce. I used to work with a Thai women whose name was Wattana and she choose Ana as an English nn.
I know one Yolanda, my age (20). She's very sweet and kind and considerate. Her nn in Yola. And to answer your question, I think it's a fine name.
Pixie, Gemini, Candy, and Enn. Seriously?? I have friends and acquaintances from China too. Their english names are Sophie, Jolina, Alice/Elise (not sure), Grace, etc. Hearing about Pixie, Gemini and other made me somewhat speechless.
Yolanda to be antiquated.