I don't mind it for pace, but I don't recall it coming that easy when I read the LN, even though she was grossed out by it... I think they needed to do a better job of illustrating that plenty of time had passed, or that she was at her limits and at her wit's end for her to "indulge" in such an act. That's how I recall it, but my memory may be failing me.
So I'm a Spider, So What? is more of a Lit-RPG type of series where there's a lot of focus on the leveling up process, though it's pertinent for the full series, I very much doubt the anime can go the route of spending the same amount of time in that process, particularly early stages. Though I wouldn't be surprised if the first 12 episodes are focused on the grind as she goes about fighting stronger opponents.
As Slime is mentioned, for obvious reasons due to similarities, that story doesn't feature much of the struggle to get stronger, this one will do some power-leveling. Personally I enjoy that a lot, but at the same time i can see how reading (watching) a character power-leveling can be a bit dull as well. As I said, a lot of the charm of the series was the main character's narration/introspection and that should keep things entertaining if handled well.
Honestly, it's a shame that we're having So I'm a Spider, So What?, That Time I Got Reincarnated as a Slime, and Mushoku Tensei: Jobless Reincarnation airing in the same season.