Li Sushang has multiple battlesuits (forms) so just saying her name isn't enough. In general it's always best to refer to the battlesuit name or abbreviation. You can search the latter in the pinned glossary in the beginner help channel.
When looking at other guides, try to understand the underlying reason and don't just accept advice blindly. Also check the date. The guide you looked at might be very old.
You're probably referring to Jade Knight which is the free farmable one. The role of JK is to farm sp > cast her ult to give the team ice breach (ignore a portion of enemy resistance stats).
HoHE's previous team without her new weapon can use JK and Pardo (RC). At full gear, Shigure Kira (Sugary Starburst) actually replaces Pardo but if you're a beginner and keeping things cheap, then stick with RC. Final answer is yes you can use this but do NOT expect it to use it well in late game. This is only for temporary purposes until you spend crystals to get something better from the gacha in the future.