OK, she's in Reception, just started in fact. Remember that at that age, there will be children who have turned 5 this week, and others that were only 3 years old a few weeks ago. At this age that even 6 months is a massive proportion of their life, and so it's not a good idea to compare with others. It's really too young to tell - DD was obviously quite precocious, but though she's in top sets, she plateaued aged about 8-10 seems to be developing again now. DS is younger and frankly we thought he wasn't too bright for a very long time. Now he's considered "extremely bright" by school.
This may sound counter-intuitive at first, but: Growth mindset and resilience is one of the best things you can give her. This means encouraging her not to get upset about when she gets things wrong, but sees them as opportunities to grow. Praise effort rather than success. Otherwise you end up with a perfectionist child terrified to try something hard in case they get it wrong. Show her how you get things wrong and that it's ok, and then pick yourself back up and try again. In real life it's often that resilience that leads to success.
Books and reading. And talk about what's in them, ideas etc. Eat your evening meal together, at the table if you have one, and talk about life, ideas etc. They start picking up all sorts at school, and you can turn a lot of things into a "teachable moment". If you don't know the answer, that's fine - excellent even, because you can show her how to research answers in books, library, online. Above all make reading fun. A child can grow up in a tiny flat with no resources, but the world will open up for them through books if they love reading. Once they're reading chapter books you would not believe how much random information goes in their brains and sticks.
Maths - as others have said, baking, looking for numbers out and about. Any opportunity to use numbers in real life. Car numberplate, door numbers, lift buttons, anything. Also we found the Little Orchard boardgames were good for reinforcing maths learning in a fun way as well as things like Snakes and Ladders.
Learning through play - give them scissors, glue sticks, boxes, paper etc and let them create. It's good for problem solving, creativity, and the fine motor control they'll need for handwriting.
Admittedly hard at present, but when you know what the topics are at school, talk about them, visit related sites - museums are often free. If not you can explore many online now.
Above all, love, encouragement and support from you, and that sounds like you're already on it. But do remember to show your love for her whether she gets all her spellings right, or gets them wrong. The key is the unconditional love. If you show her education is important and she can see you reading etc... that will make so much difference. But if she knows she has a safe and loving base, she will also have the courage to spread her wings.
Experience - 2 DC at primary, but I also mentor bright but disadvantaged teenagers, and I've seen how much parental engagement and encouragement can help. Even now you can talk to her about university, how it's like a big school for older children, where they can study the thing they like best - so she knows it's an option. She doesn't have to go, not everyone is suited, but let her know it's an option for her.