The conditional logic might require some tweaking, based on the exact requirement. For example, do you always want the second tile to not be resizable? It doesn't matter if you reorder it, the tile on position 2 should never be allowed to resize. If that is the case, then the above approach will work.
If you wish to target tile "B" in particular, no matter what position it is on, then you would have to identify it in some way. Here's one example: