Was at my friend's house tonight and he does have the same model as you. Basically, the DV input is for camcorders, so not relevant for this. What you can do though is, take a Scart connection out of your Sky HD box and into the DVD recorder. The recorder can then record this input on to DVDs. Scart doesn't have the bandwidth that HDMI has, therefore your video will be in SD i.e. 576p I think as it's a PAL source rather than 1080i or 1080p, so the recording itself is done in SD (NB - this is the same resolution as a standard UK DVD, assuming you have it in XP or SP mode). However, when you play this DVD back on your DVD recorder, it will then upscale this to 1080i / 1080p etc. depending on how you've set this up.
When your sis plays this back, it will play back as a normal DVD, unless she also has an upscaling DVD player, in which case, this will also upscale the content for her screen. So basically, as long as you use XP or SP recording mode, it should look pretty decent on her screen. This is all based on what I saw when my friend tested it on an HD recording he had of Casino Royale on his Sky HD box. Your best bet is to get a re-writable disk and play around with it first so you can playback what you're recording and make sure it's of a reasonable quality.
[NB - I know all this works as I've seen my friend do it, but if I've got any of the figures wrong e.g. 576p, 1080i, 1080p - let us both know as I still get confused by this myself!]