I don't know what people are on about. Marnie is a perfectly nice name what is 'whiny' about it FGS? I also love Claire although sheep like people will automatically say 'dated' as it was so popular in the 60s, 70s and 80s. But so what if it was? It's a lovely name. I prefer it to the currently popular version 'Clara'. Anyway it's only a middle.
The whole name flows fine, and again Claire is a middle name so you won't often be saying the two names together, therefore it won't be mixed up with Marie-Claire. Obviously. Jeez.