Mewis and Dahlkemper have played together on numerous teams including the national side, North Carolina Courage and Western New York Flash.
Mewis has experienced a brilliant period of form before picking up an injury in the USWNT's friendly against Colombia in January, scoring her first career hat trick in the first game against the South American side and featuring regularly for City.
"The sky is the limit for Sam," Dahlkemper told ESPN. "She is a force to be reckoned with.
"She has really fine tuned her skills. She's always had all the qualities -- physicality, speed, tech ability.
"I've seen her fine tune her tactical awareness and position on the field through studying film all the time and I think that's so special to be able to see her growth hands on.
"She is one of the best players in the world right now no doubt and she has emerged as this leader on the team and I'm just so proud of her. She's playing amazing soccer right now. She's so fearless, you can see it on the field."
The defender said it had been a "whirlwind" as she just arrived in England last week from the USWNT's January camp but that she was happy to get her first minutes under her belt.
"It was a lot of learning in a couple of days. Obviously the system, the way we want to play both offensively and defensively," she said.
"I was able to pick up most of it fairly quickly but I think it is fine tuning the little things now and continuing to learn and grow and help the team in anyway I can."
On the differences between the NWSL and the Women's Super League Dahlkemper said she hopes she will be able to challenge her new teammates with all she learned in the U.S. league.
"In the NWSL it is very transitional, very quick. Everyone is so athletic and fast," she added.
"I think [I'm] just hoping to bring things that I've learned in the NWSL and the different style of play over but also be able to adjust and open to learning how the girls play here and how the teams play and really gathering ball possession and technically and tactically ironing out all the details.
"That is something I've definitely noticed over my first week here that technically and tactically everyone is at such a high level because I think over in the NWSL it's a bit more physical and transitional and so I think it just different but it is good."