Nocaffeineforlevi asked so this is a list of other Doctors that Yaz could have seen 13 regenerate into, and how well she might have taken it.
Peter Cushing) See 1st Doctor, except this one might actually go back to check on Susan sometime.
The Morbing Time Doctors) Insufficient data.
The Watcher) I don't think 13 could regenerate into this guy since he's more like a type of regenerating, but at some point while regenerating the AI Doctor from The Power of The Doctor could walk out from inside Yaz, turn into the Watcher, and then merge with 13?
The Valeyard) Announcing that he is sorry to have arrived one regeneration late, the Valeyard proclaims that he is the manifestation of all of the Doctor's evil and that he shall destroy the Time Lords and take over the universe. When Yaz points out that the Time Lords are already dead, the Valeyard is left a little stumped. He mentions wanting to kill his past self and steal his remaining regenerations, and Yaz points out that he's got plenty of regenerations left. Left without much to do, the Valeyard decides to go on a few normal adventures while trying to make a plan, and Yaz sticks around for a while before eventually pulling the same trick she pulled on the Master.
The 9th Doctor of Fatal Death) He's looking to settle down and could well propose on the spot which would seem good at first, but I think Yaz loves the Doctor for adventure's sake and
The 10th Doctor of Fatal Death) Scroll down a bit and read what I've put for the Shalka Doctor.
The 11th Doctor of Fatal Death) Raw deal. He does seem a bit accident prone though, and she might just start encouraging the Doctor to take risks in the hopes of a mulligan.
The 12th Doctor of Fatal Death) Suave, good looking, maybe Yaz' type, and he'll make a few remarks about how she ought to stick around and find out. When eventually their ways parted after a few years of dashing adventure he'd offer her 13's jacket as a keepsake.
The 13th Doctor of Fatal Death) The 13th Doctor has just regenerated into a version of herself that is openly a lesbian and will, in the first moments of regeneration, start buzzing her sonic screwdriver.
Yazmin Khan is going to have the most awkward, fumbling, and sensual sex she will ever have in her life. I guarantee that she's heard the "3 settings" line in a dream or a fantasy that came into her head whilst using a similarly versatile tool.
The Shalka Doctor) One might think that this could be a similarly good time as the 8th Doctor but it would be more as a companion than as a partner. The Spy Master being rebuilt as a robot would be ironic after his stint as Master of the Cyber Masters and Yaz would take care to constantly annoy him. Give it one season and then Yaz leaves to join an archeological society alongside River Song and other veteran adventurers.
Metacrisis Doctor) Pouring her excess regeneration energy into Chris Chibnall, the 13th Doctor regenerates into a naked David Tennant, whilst Chris Chibnall regenerates into a clothed Jodie Whittaker. Naked David Tennant abandons them both on Gallifrey next to the TARDIS bay and tells them to just take their pick, no need to grow one They bump into Mrs Flood and the Master, both of whom are also out shopping for TARDISes, and the three of them reflect that they should probably do something to make sure nobody else decides to come loot the Citadel.
The War Doctor) See the 12th Doctor but this time it doesn't progress forwards as much. His heart would be weary and heavy, fully aware of just how many children on Gallifrey got blown up by the Master twice. Yaz leaves him after wishing him well and suggesting that he could always go back in time and save all the Time Lords again, seeing as there isn't really a time lock or anything this time.
The Fugitive Doctor) Yaz wakes up at home in her bed, exhausted and aching from the night of her life. Atop her bedside table is an empty fob watch, a set of coordinates and a date inscribed on the inside lid. Will the Fugitive Doctor return? She must. But for now she must go, for she is too mysterious and too dangerous to know for long, and she is already engaged to another who has waited long enough. Years later, Yaz stands outside the doors of a barber shop...
Brendan) The Doctor finally confides his true name with Yaz, who is bemused to learn that it has been "Brendan Who" all this time. Still, he's attractive, he's a policeman so they can bond over that, he's nice, and they'd have a lovely time together right up until Yaz stars in 73 Yards. She tells Brendan not to step and he avoids disturbing the magic circle, only to fall off the cliff instead.
The DoctorMaster) She literally just fixed this. How annoying. The arrival of a version of the Master that has just regenerated into an exact duplicate of the 13th Doctor further confuses matters. The DoctorMaster is annoyed by the MasterDoctor, who reveals her heroic plan has been to ruin the Master's regeneration by saving multiple worlds from disaster while saying that she, the Master, was the one who saved them. This episode is called The Power of the Master, and ends with both time lords competing to prove which of them is the real Master by dominating Yaz with their powerful and evil hypnosis.
