May have got my manager pregnant

So basically I slept with my manager after a works party about 3 months ago.

I'm 23, shes 36. We've worked together for about 2 years and always had a good relationship. She's very attractive and weve always had banter and maybe flirted a little. It's common knowledge that she has marriage problems, shes always moaning about her husband and I dont think they have much sex anymore. They also have 2 kids already together.

We were both pretty drunk at the party, she was looking very good so we just started dancing together and she went outside to smoke and I followed her, we ended up getting an uber back to my flat where we had sex.

This week, she announces shes pregnant and had her 12 week scan. We had sex just over 12 weeks ago. So im very dubious about it being her husband's as she says. We didnt use protection but I presumed she would have been on something.

I have spoken to her but she's 100% it's her husbands and "it cant be mine" but hasnt said anything more.

I just dont know what to do.