It's just the next logical step really.
In the comics Faith has now been free and single for years while Buffy has simply bounced back between her two vampire exes with no resolution in sight. So the writers have a choice; either its Angel's 'turn' now after Spike and her end (IF they do end.. and yay for Buffy's agency!) or something new should happen with Buffy's love life.
But why should that 'something new' be Faith?
1) Introducing new characters in the Buffy comics has had very mixed results, your're just not going to have time to introduce a new character. who can also be a love interest, who's also going to be that interesting to a large section of the fandom.
The only new Scoobie romance that has worked so far long-term has been Xander/Dawn- both characters introduced back on the show. So imo the 'new' someone has to be someone from the show. Just for the sake of investment by the fandom.
2) and more importantly, they have a complicated history that can be mined for interesting drama and dynamics. Creating new stories equals better than recycling old stories.
3) Finally Buffy still seems to feel 'alone' a lot of the time, still searching for happiness and that somebody to make her feel whole. This has actually been a trend of hers that's been growing ever since her first death end the end of Season 1 but that realy hit home after the slayer spell at the end of S4. Even when surrounded by family, freinds, a thousand 'just like her' slayers, she can still feel totally isolated.
I think that's because Buffy 'came back', which no slayer has done before, and contiuened on being alive and kicking ass, so a apart of her went into Kendra and then quickly passed on into Faith, and there is has stayed. That's why they are forever linked; by dreams, by calling, whatever.
Faith still has that missing part of Buffy.
It's also worth noting that they've been separated in the comics for large amounts of time and distance, not really coming together much.
When Buffy says to Xander in early S8 that she feels alone, unconnected to all the other slayers, Faith is thousands of miles away, conspicuous by her absence.
LaterBuffy and Faith clash in battle, and then a issue or so afterwards Buffy is trying to 'connect' with Satsu (because she knows how Satsu feels about her thanks to 'the kiss'). The timing of that is somewhat interesting I have to say.
Then Faith is off with Giles for months, away from the main plot happenings, but when they reunite on the run from their amassing enemies it Faith who comforts Buffy in the midst of chaos in Tibet...and is promptly abducted by Twilight before any upcoming final confrontation. What was he so concerned about?
Then during the world-ending apocalypse Faith leads the charge, scythe in hand, without any hesitation. Like the end of S7 all over again. If Bufyf is unavailable Faith willls tep into the breach, no questions asked.
In the devestating aftermath Faith is sympathetic to Buffy not only about Giles' will but also about taking Angel off her hands. An easing of some of that immense guilt I'm sure.
So the writers could have been laying the groundwork for some sort of reconciliation in the near future.
Buffy needs to do what Willow and Xander are allowed to do, move on from past lovers without looking back. Willow has moved beyond Tara and Xander is now also with someone new. Angel, Riley and now Spike have had their time, plenty of chances and now something fresh needs to occur.
Finally a note on what each love interest imo has meant to Buffy.
Angel made Buffy feel special. After 100 years she was his salvation. That's some powerful romance right there for a teenage girl, no wonder she thought it was meant to be and didn't consider the future. But it was a first love that cannot grow because of the whole vampire/curse thing. They both must move on.
Riley made Buffy feel normal; the sensitive-yet studly boyfriend who could picnic with her and play beach football, who could also patrol with her at night with his super-special army training. He should've been the perfect match but he couldn't 'connect' to her properly. So Riley was left behind.
Spike made Buffy feel loved. He was the demon/guy who never stopped loving her even after he went through momentous changes in his own life. He was there for her at times when no-one else was (not always in the best way but still), and yet their connection was fleeting at best and bourne of trying/difficult circumstance.
So if/when it finally happens Faith will make Buffy feel, possibly for the first time ever, complete. She will that missing part that finally returns to her.
End ramble. 🙂
