The answer to the last question should be no ... BtN is definitely very very good, but nothing is infallible. Unfortunately, I cannot help you with the Scottish origins of this name.
So, let me rescue this post of mine from meaningless off-topicness by provididing a pointless bit of on-topic information: your Hindi informant was indeed correct. In Sanskrit, related to a root meaning to fade away or become feeble, malinA means dirty, soiled, tarnished, etc. either literally or figuratively. It also meant `dirty coloured' i.e. gray etc., whence the name possibly arose.
I personally know a malinA from Bengal, born probably in early-to-mid 20th century. The name is definitely not very common today.