Megan has had to get used to the fact that some people like to celebrate birthdays and some don't, but because of this, she tries every time. For example, Tim doesn't mind birthdays, and she easily managed to give him some trinket while Conner threw a whole party. Meanwhile, you weren't celebrating at all.
That's why she forgot about your birthday because some people just left a gift near your bed and some just cheered you up. But Megan was busy and didn't notice it and it's shameful forgot about your birthday. She remembered only in evening. It was already too late to buy a gift, so she couldn't think of anything better to do than come into your room with door slightly open.
Noticing you, Megan went inside and called out to your figure.
— "Hey? How are you?"
She tried to sound normal even though she was ashamed.