Amazon sell Feliway, as do many online pet stores. In the UK, vets generally stock it too (at least mine does ), so that's another place to try. Buying it online is generally cheaper, though.
If Lily seems really stressed out, she might benefit from a nutrition-based calmer (such as Composure or Zylkene), at least for a while. I had Asha on a calmer in the early days of introductions, and it did seem to help her a bit.
Asha took quite a while to go back into the kittens' room, and even now doesn't spend much time in there - she mostly goes in to use their litterboxes! (They use hers all the time, and 5 of the 6 boxes are now shared by all 3 cats).
Getting Lily and Jethro playing at opposite ends of the same room could help things along too, so that's worth a go. It backfired with my guys because the boys, especially Shenka, growl a LOT at their toys once they've caught them, and the growling freaked Asha out So long as Jethro isn't an enthusiastic play-growler, you should be fine
If Lily seems really stressed out, she might benefit from a nutrition-based calmer (such as Composure or Zylkene), at least for a while. I had Asha on a calmer in the early days of introductions, and it did seem to help her a bit.
Asha took quite a while to go back into the kittens' room, and even now doesn't spend much time in there - she mostly goes in to use their litterboxes! (They use hers all the time, and 5 of the 6 boxes are now shared by all 3 cats).
Getting Lily and Jethro playing at opposite ends of the same room could help things along too, so that's worth a go. It backfired with my guys because the boys, especially Shenka, growl a LOT at their toys once they've caught them, and the growling freaked Asha out So long as Jethro isn't an enthusiastic play-growler, you should be fine