Not a bad idea but you have to consider some factors working here. The most important factors are, Is she willing to handle BTC? Is she interested in that? Will she get benefit from that? Does she take permission from her husband? And which types of gift can make her happy? If you don't know all the answers then you can discuss them with her frankly. A very good piece of advice is don't try to make or keep any relationship with a married person, you can pray that The Almighty may make her happy and safe.