Would and SSD or RAM be the better upgrade in this situation? I feel I'm making this post more for validation than anything, but I want to get some of your opinions as well.

My friend contacted me the other day asking how she could make her MacBook Pro run a bit faster. I had her send me a screenshot of what she has and it's a Mid 2009 MBP with 4GB of RAM. I had her send me a screenshot of activity monitor and it shows she was using 8 MB of swap. In my mind, she is going to see a better performance boost from upgrading to an SSD instead of RAM, here's why:

Her swap memory is already pretty low. Now, she is running 10.10.1, which is more RAM hungry, but that's the beauty of an SSD. Even if she does need more RAM, her swap will be much more efficient because it's on an SSD. And, when it's not needing it, any read/writes will be exponentially faster than the current 5400 rpm 320 GB drive she has now.

She talked to her brother who said to her "upgrading to an SSD you won't see a difference unless you game." Which I then let her know is complete and utter.... you know. So I decided she could upgrade to 6GB of RAM for cheap and then get an SSD all for under $250. She told me that would be her ceiling. 

Tonight she told me that because of what her brother said and another friend of hers said she is going to get a 1TB spinning drive and 8GB of RAM but she still wants me to help install it. I think a 1TB is honestly a terrible idea since that will most likely make read/writes slower, but that's just me.

So tell me... do you think my logic is faulty? Is more RAM really going to be a huge upgrade for her? Or am I making sense by thinking "if swap is needed, it's better it be from an SSD than get more ram that you aren't using in the first place?"
Your logic is sound. Just something to keep in mind is that while yes swap is much faster on a SSD, it is still much slower in respect to RAM and both should probably be upgraded. But yes she would see the most improvement by going to a SSD

Just as a side note 10.10.1 will try to pre-cache as many things as possible in RAM so apple uses 'memory pressure' to reflect the systems demand for RAM.