1 day of heavy bleeding/clots

Hi ladies,
I'm typing for a friend of mine who is really worried about herself.
She got her period normally 2 weeks ago, everything was as it should be!
Well, she woke up yesterday, got out of bed and it felt like she had peed in her pants. She ran to the toilet and it was a very heavy bleed.. then she thought, what's weird, am I on my period?
Well, she put on a maxi pad and went to work and she had to change it 2 times in 3 hours because it was bleeding very heavily. When she went to the toilet for the 3rd time, she had a very long mucus plug/clot when wiping.. after that she only bled a little bit more and it was completely over in the evening. This morning she got up and there was no blood to be found anywhere but her breasts hurt a lot today.. she is really worried about herself... has anyone experienced this before? Or what it could be?
They want a baby!
Greetings