I think I’d find a regular novel harder, actually. For an IF I get to write a narrative landscape that the reader gets to explore; all the ways through need to be fun, but no single one needs to be perfect. In a non-interactive novel, I’d need to be confident that the route I’ve picked through the potential landscape is the single best one – not just that the prose is the best it possibly can be, but the plot and characters too. That would be a lot more stress-inducing for me. And I’d end up scrapping so much good written material that gets to stay reader-accessible in an IF.
And sure, IF is longer, but I’d be long-winded in long-form no matter what. I’d be like Raymond Feist or Terry Brooks, spinning out endless sequel series exploring different corners of my world, or Marilynne Robinson falling so in love with my characters that I rewrite the same (great) novel four times. With XoR, the “alternative perspective” sequels are part of the original. 
I’m not enough of an IF nut to claim that I don’t sometimes get tired of wrapping up an extended choice block – not because I ever think “no one will read this” (because after a decade on the forum having people quote my stuff back to me, it’s clear that someone’s going to find every obscure corner) but because in any fiction, there are going to be some bits that are more of a slog to finish. My unfinished novels had plenty of stretches that were a drag to write.
I think this is absolutely right. If your friend wants to create an experience where she as author is fully in control of the way the story rolls out, then a novel’s the better way to go. If she likes the idea of a story that she co-creates with the reader, or an explorable story that has no single best way through, then go with IF.