I happen to really like
Blossom. It's on my GP list, but only because my husband is not a fan. I would use it in a heartbeat.
I also happen to like
Mona. I think it is one of those short and sweet antique charmers. Plus, it sounds lovely with
Blossom.
If
Susannah,
Blossom and
Mona all have meaning to you - and you and your partner like/love it, I say you found a winner!
The overall feel is quite feminine and fresh, but there is nothing common or trendy about the name at all. I am a fan.
The flow is a bit off for me, but that is because I have particular preferences when it comes to syllables and such. As a whole, it works and is unexpectedly quirky and fun. Good job.