You don't need to do anything :)
First of all the guidance increases to 2 hour sessions once they are over 4 weeks old, so they haven't actually gone over guidance. It's only up to 30 minutes for the first 4 weeks. And that is probably quite conservative if your baby was full term, healthy and not a low birth weight (under 5lbs 8oz), especially if you have a car seat which has some kind of padding or feature to flatten out the curve of it for newborns, which most modern car seats do have. These guidelines are also approximate - it's not like it's safe up to the 119th minute and then suddenly becomes risky at the 120th. Around 2 hours is unlikely to pose a risk to a healthy 5 week old.
Secondly if it had caused her any harm it would be immediately obvious. The risk of being in a car seat too long is that they can place babies in a position where it's hard for them to get enough oxygen in through normal breathing. This over time reduces oxygen saturation levels. That isn't harmful in itself. It's OK to have slightly lower oxygen sats than normal. The problem comes when it happens over a prolonged time and they drop too much, as then oxygen flow is being reduced to the brain etc. If this had happened it would have been immediately apparent when they took her out of the seat. The fact that she was fine when they did take her out means that no harm was done and you don't need to get her checked over. As soon as she is out of the seat her oxygen saturation levels (if they were compromised, which they might not have been at all) will return to normal in a very short space of time, seconds or minutes.
It's not overreacting to be aware of these guidelines, but it is helpful to understand why they exist and put the risk into perspective. Car seats are designed for crash safety, they aren't general seats designed for babies to lounge and sleep in, although they are sometimes marketed for this purpose. It isn't a problem to let a baby sleep in a car seat occasionally but it is a good idea to keep these time guidelines in mind. Babies have sadly died or had adverse experiences from being left in their car seats for too long. It's rare - it has to be the "perfect storm" of circumstances but keeping the time limited to 2 hours (30 minutes under 4 weeks) minimises this risk and means that you can use the car seat to prolong a nap or easily transfer between car and stroller etc without worrying about it.
It's OK that it happened twice in one day. In terms of oxygen saturation, you could put them in the seat for 2 hours, out for 5 minutes, in for 2 hours, out for 5 minutes all day. This wouldn't be recommended because babies need to lie flat in order to stretch and practice rolling and moving around, plus of course you'd need to feed and change them, but in terms of oxygen saturation that would be fine. So one off long journeys for example are fine, but using the car seat every day as a replacement for a pram and also a seat at home and never holding them would be damaging (in a different way).
These risks don't apply only to car seats but to any product where the baby is placed in a curved position. But car seats are unique with the 30 minute first 4 weeks rule - this is because of the very upright position within the car and the movement in the car and is a relatively recent discovery based on research done in 2016.