My top suggestions for Solo Women Travelers are to arrive safely and to enjoy all Guatemala and the Mayan Culture offers.
Most travelers arrive by Air at Guatemala International Airport and then will need transportation shuttle service to either Antigua, Lake Atitlan, or other Guatemala Tourist deist nations like Xela for Spanish School.
I recommend choosing a know shuttle service, check out their website and social media. I recommend https://www.facebook.com/guatemalasurmesure. You can choose between a private Shuttle or a Collective meaning you share the shuttle.
Do Not Rent a Car, you will find driving, parking, and dealing with traffic not worth what you think you will save on paying for Shuttles.
Choosing a Hotel in either Antigua or Lake Atitlan. For Antigua, this group owns several hotels with varying price ranges and options. https://www.antiguahotelsolutions.com/ For Hostels check out Hostel World for the best reviews. For Airbnb, choose wisely, check all references, and do not be fooled by the pictures, ask a lot of questions.