nepesh is right me lovely.
It's usually a sign of spirit being around. soooo you say it happens when you come on here. Makes sense. Because your talking and thinking about spiritual matters you've opened up your chakra's and have connected, allowing spirit to come through. Now what you have to realise is it's only a thought away. So you could be reading a book, having a convo on the phone, watching a tv programme. Whatever it is your doing can open your awareness up so hence the flowers :) .. now your first thought was your grandmother .. why can't you contact the home she's in? or anohter famly member? xox