You have to assume Taylor doesn't think she warrants a place.
White started the season out of the team quite a bit and is now a featuring player, so we know Taylor will change his mind on someone if he thinks they're worth it.
Mewis came in and cleared out Scott, so we know Taylor is willing to drop someone for a more impressive player.
Lavelle isn't in the team (yet), so Taylor mustn't think she's the best fit (right now). The players currently playing are of a high level atm.
From what I knew of Lavelle before she joined City, was that she's an awesome dribbler but she's not the best in terms of possession retention on a wider level, and isn't the best tactically. It's possible that she just needs more time to settle in, similarly to players like Cancelo for the men's team. Of course, unlike Cancelo, it's very possible Lavelle won't be here next season to reap the rewards of settling.
Hopefully she comes good at some point before she goes, because the talent is off the charts. If we're still in the CL and battling for the WSL then even for a small number of games a top form Lavelle could be a difference maker.