Well...that's why the italicized "should". Because they're are times when that doesn't work. In your case I can't understand why it wouldn't. The space is unallocated/free. It should make no difference if that unallocated/free space is contiguous with any particular partition on the drive. Especially since we're talking about an SSD. You should be able to extend any non-boot volume/partition(or, in theory, even any boot volume/partition not currently in use) on the same drive to encompass the unallocated space available. It also shouldn't matter how large or small the available unallocated space is.
One thing I would try is when it asks you to select the amount of space in MB to extend the volume, select an amount slightly less than it says is the maximum available. What I've found is Disk Management can be wrong about the maximum available space. It will tell you X is the maximum amount of space available, when X amount is actually too high. Then when you try to enter that amount of space exactly you'll get a warning saying that's too much and it can't be completed. So if it's saying for instance that 1020MB is available, but that's giving you a warning when you try to extend the volume by that amount. Try selecting 1019MB and see if it works. If it still doesn't work, keep bumping it down 1MB at a time until it does. That should, again should in italics, correct for Disk Management being retarded about reporting the actual amount of space available. Sometimes Disk Management can be WAY OFF. So it might take A LOT of tries to get to the correct size. I just tried doing this same process to make sure I knew what I was talking about. I tried to shrink a partition so I could extend it(the same partition) using the newly created unallocated space. Disk Management kept giving me the warning about the amount of space it said was available to shrink the volume being too much. WTF? It said 16102MB was the maximum available. Much trial and error revealed the actual maximum available space to be 9222MB. WAY OFF! If it can be wrong about that then I can easily imagine it being wrong about the maximum available amount of unallocated space.